Re-entry Sightings and Debris Recovery of 2008-010B

Spain - 2015 November 03 UTC

Ted Molczan - 2015 November 19

 

Major Revisions

2016 Mar 11 Added discovery of cylindrical COPV tank with titanium liner near Isso (2.2) (A.6)
2015 Dec 06 Added Appendix A: Photos of suspected debris.
2015 Dec 05 Delayed time of passage of estimated trajectory additional 30 s, to shift ground track west 11 km.
2015 Nov 30 Added analysis of image of suspected smoke trail
2015 Nov 22 Added video of fireball taken from Almansa (Alicante) (2.1.3)
2015 Nov 20 Added description of re-construction of fireball sighting by Sr. Ruiz Gomez

1. Summary
2. Fireball sighting and debris information
    2.1 Fireball sightings
    2.2 Suspected debris
3. Prime suspect is re-entry of 2008-010B
    3.1 Debris locations reveal approximate orbital inclination
    3.2 Search for objects in matching orbits that were near decay
    3.3 Recovered spheres consistent with those of Atlas-V Centaur stage
4. Orbital decay analysis of 2008-010B
    4.1 Satevo decay propagation analysis
    4.2 GMAT propagation
    4.3 2008-010B correlates with debris locations
    4.4 2008-010B correlates with fireball sighting
    4.5 Analysis of image of suspected smoke trail
5. Conclusions
    5.1 What's next for the debris?
6. Acknowledgments
Appendix A: Photos of suspected debris

1. Summary

A re-entering Centaur rocket body was the source of three COPV (composite overwrapped pressure vessel) spheres, discovered in Spain following pre-dawn sightings of a fireball on Tuesday, November 3, 2015. The Centaur was the upper stage of the Atlas-V rocket launched on March 13, 2008 from Vandenberg AFB, that carried the NROL-28 payload for the U.S. National Reconnaissance Office. The Centaur had been discarded in a highly elliptical orbit of the Molniya type. It was more than 12 m long, 3 m in diameter, with an empty mass of 2,100 kg. It had the international designation 2008-010B, and the USSTRATCOM (U.S. Strategic Command) catalogue number 32707.

Analysis of recent orbital data revealed that 2008-010B should have re-entered on or about November 3rd, and that if it came down over Spain at the time of the fireball sightings (about 7 AM CET, 6 UTC), it would have passed close to the location of four of the five suspected pieces of space debris reported to-date. The Centaur in question is known to have carried three spherical COPV tanks, of the same diameter as the three found in Murcia, in the area between Mula and Calasparra. The spheres and the large suspected debris fragment found near Pozorrubio de Santiago (Cuenca), were found within several kilometres of the estimated re-entry ground track. The densest fragments of re-entering objects normally fall within about 10 km of the ground track. The 4 m long metal strip found near Elda (Alicante), was 80 km from the ground track of 2008-010B, well beyond the distance that the wind could normally have carried it; therefore, probably not related.

The case was solved by detective work. USSTRATCOM's Space-Track web site provides predictions of most upcoming decays, as well as historical information, but it listed no re-entries that could explain the events in Spain. This was a clue that the object had been related to a military mission, because USSTRATCOM seldom provides orbital or re-entry data for U.S. military and intelligence gathering satellites, and those of several of its allies. The lack of any official information made this re-entry more challenging to identify than usual. Analyzing clues provided by the fireball sightings and the recovered debris, revealed the specific orbit from which the re-entering body had descended. It was inclined approximately 64 deg, and travelled toward the south-east over Spain on 2015 Nov 03 near 06:00 UTC. Independent sources of orbital data were consulted to find an object that matched this very well constrained orbit.

The author is a member of a small, informal group of amateur astronomers, who specialize in tracking satellites in unpublished orbits. They share their observations and analyses of several hundred such objects via the SeeSat-L mailing list. On October 15, Scott Tilley observed a satellite that he could not immediately identify. Mike McCants identified it as Centaur upper stage 2008-010B / 32707, in a 63 deg orbit, last knowingly observed in February, when it was far from decay. Mike fit an approximate orbit to Scott's observations, which revealed that it was decaying rapidly, which together with the 63 deg inclination matched the description of the suspect sought in the investigation of the re-entry over Spain. The hobbyists did not observe 2008-010B again after October 15, so to learn its fate, the investigation turned to another independent source of orbital data.

Russia's International Space Observation Network (ISON) conducts scientific research into high altitude orbital debris. Its global network of telescopes has detected thousands of small debris fragments that are potentially hazardous to spacecraft. Cameras that can see faint debris, inevitably detect satellites and rocket bodies. ISON's data analysis partner, JSC Vimpel, distributes orbital data on 1,700 newly detected objects, via its web-based portal. The majority of those orbits are not found in USSTRATCOM's public database. The data has not been correlated with known objects; however, the author and his colleagues have previously identified a number of U.S. military objects of interest to them, including 2008-010B. ISON had observed it frequently during 2015, and its data confirmed that by October it had been rapidly approaching decay.

On Nov 14, the author alerted SeeSat-L to the results of a quick analysis that showed a possible correlation between 2008-010B and the recent events in Spain. A subsequent more in-depth analysis confirmed the correlation, which together with the discovery of the three spheres, that match the number, size and construction of the ones carried on the Centaur, form a strong circumstantial case.

Section 2 documents existing reports on the fireball sightings and the recovered debris, which form much of the evidence of the case. Section 3 explains how the evidence led to the 2008-010B re-entry hypothesis. Section 4 reports the orbital decay analysis. Section 5 states the conclusions. Section 6 acknowledges those who assisted this study.

2. Fireball sighting and debris information

This section documents the known reports of fireball sightings and recovered debris.

2.1 Fireball sightings

Re-entry fireballs look similar to meteoritic ones. Their key distinguishing characteristics are their much slower speed, and nearly horizontal flight. Meteors seldom are observed to break-up, but this is almost always a feature of re-entries. Observers see a swarm of bright lights, each with a meteor-like tail, moving along the same path. The key information for analysis is the time of the sighting and the direction of travel.

The fireball suspected to have been the source of the debris occurred in bright morning twilight, so it was not as prominent as it would have been in a dark sky, which probably explains the scarcity of sighting reports.

2.1.1 Las Cumbres

The earliest reports of fireball sightings came from the vicinity of Calasparra, where three COPV spheres subsequently were found. Several newspaper articles mentioned the sighting of 7-8 fireballs early on the morning of Tuesday, November 3 - the same day that the first sphere was discovered. A November 10 article in La Verdad reported some useful details:

«Vimos un conjunto de bolas de fuego. Eran siete u ocho». Es lo que afrman con vehemencia los dos vecinos de Calasparra que supuestamente podrían aclarar las causas por las que han sido localizadas dos supuestas esferas espaciales en la misma semana y con una distancia entre sí de solo 12 kilómetros. La primera la encontraron dos pastores, el pasado martes, en el paraje de Los Llanos del Cagitán de Mula. Ese día, estos vecinos iban andando como cada mañana por el paraje de Las Cumbres, cuando, a las 7 horas, esas supuestas bolas envueltas en llamas «pasaron por encima de nosotros. No hemos visto nada igual jamás».
"We saw a group of fireballs. There were seven or eight. " It's what two neighbors in Calasparra firmly claim who could supposedly clarify the reasons why they (the spheres) have been located in two alleged areas in the same week and with distances between them of only 12 kilometers. The first was found by two shepherds last Tuesday in the vicinity of Los Llanos of Cagitán, Mula. That day, these neighbors were walking like every morning at Las Cumbres, when, at 7 am, these alleged balls wrapped in flames "passed over us. We have not ever seen anything like it. "
Las pudieron observar surcando el cielo apenas siete segundos. «Sentimos un poco de miedo, porque no sabíamos qué podían ser ni dónde iban a caer». Después de perderlas de vista escucharon un estruendo. «Cayeron sobre el Cagitán y las zonas adyacentes», detallan estos calasparreños que no quieren desvelar sus identidades por el revuelo mediático que sacude estos días el municipio.
They could observe (them) crossing the sky in just seven seconds. "We were a little scared because we did not know what they might be or where they would fall." After losing sight (of them) they heard a roar like thunder. "They fell on Cagitán and adjacent areas", was the description given by these people from Calasparra, who do not want to reveal their identities because of the media frenzy that shakes the town these days.
The sighting was at about 7 AM CET (6 UTC), from Las Cumbres. The witnesses reported that the fireball headed toward Los Llanos del Cagitán, less than 10 km to their southeast, where the first sphere was discovered. After they lost sight of it, they heard a “roar like thunder” (“estruendo”), consistent with a known phenomenon of re-entries, resulting from sonic booms of fragments below about 50 km altitude. Knowing the duration of the delay before this sound was heard, would help to decide whether it was a sonic boom.

2.1.2 Almería

On November 3, in Almería, minutes after 7 AM CET, amateur astronomer José Luis Ruiz Gomez had just completed an observing session. As he prepared to return indoors, he spotted a fireball, at about 7:03 AM CET (6:03 UTC). He watched it for about 30 s, during which it fragmented three times. He spotted it low in the north, traveling "somewhat approximate northwest-west to southeast-east." He reported this before the Centaur hypothesis and trajectory analysis had been made public. Section 4.4 presents his reconstruction of the sighting, aided by the re-entry trajectory data.

Sr. Ruiz Gomez attempted to photograph the fireball in progress, but it faded from view before he could steady his camera. At 06:10:45 UTC +/-1 s, he photographed what has been identified as a smoke trail remnant of the re-entry fireball, that lingered in the bright twilight sky. It is the short, roughly horizontal white cloud, at centre-right of Figure 1. The analysis is in Section 4.5.

[Probable smoke trail remnant of re-entry fireball]
Fig. 1.  Probable smoke trail remnant of re-entry fireball. Courtesy R. Gomez.

2.1.3 Almansa (Alicante)

Sr. Ximo Alvarez made a cell phone video from a highway in Almansa (Alicante). The reported time of the sighting was 2015 Nov 03 at 7 AM CET (6 UTC). It is a bit dark, but adjusting the brightness reveals a string of several lights moving from right to left, seen between clouds in the morning twilight.

2.2 Suspected debris

The following table summarizes the suspected pieces of debris of the fireball, reported to-date.

Table 1:  Location and Physical Properties of Suspected Debris
Object Date Found Location Approx. co-ordinates Dimensions Mass
Sphere 1 2015 Nov 03 Los Llanos del Cagitán (Murcia)
38.17 N, 1.59 W
65 cm dia. 23 kg
Flanged pipe or duct 2015 Nov 07 near Pozorrubio de Santiago (Cuenca)
39.81 N, 2.90 W
40 cm dia. pipe or duct elbow 20 kg
Sphere 2 2015 Nov 08 Villa Vieja (Murcia)
38.25 N, 1.69 W
65 cm dia. 23 kg
Metal strip 2015 Nov 10 Las Barrancadas (Alicante)
38.47 N, 0.85 W
4 m X 0.2 m ?
Sphere 3 2015 Nov 15 near Sierra del Molino (Murcia)
38.23 N, 1.64 W
65 cm dia. 23 kg
Cylindrical tank 2016 Mar 08 near Isso (Albacete)
38.46 N, 1.83 W
80 cm dia., 1 mm thick 10 kg

The co-ordinates are predominantly those of places reported by the news media to have been proximate to the debris, probably accurate to within a few kilometres. We are seeking data closer to GPS accuracy, or at least 0.1 km.

Most of the initially published physical data was imprecise; however, Vicente-Juan Ballester Olmos found a Nov 12 article in El País, which provided information on the mass and measured size of the first sphere found:

Con aproximadamente 15 kilos, 20 como máximo, la esfera de origen espacial hallada en Mula (Murcia), pesa como una bombona de butano vacía, explica a EL PAÍS Juan Antonio Madrid Mendoza, director del Centro de Referencia Nacional de FP de Cartagena. "No la hemos pesado porque no disponemos de una báscula de ese rango", anade. Lo que si han hecho en el centro es medirla. Tiene un perímetro de 205 centímetros, su diámetro es aproximadamente de 65 centímetros. "Lógicamente ya no es una esfera perfecta ya que, al impactar con la Tierra se deformó, por lo que se puede decir que es un elipsoide más que una esfera", continua Madrid Mendoza refiriéndose a la primera pieza encontrada, que, explica, es la que conoce mejor porque la manipulo para protegerla y evitar su deterioro.
Weighing about 15 kilos, 20 at most, the sphere from space found in Mula ( Murcia), weighs about as much as an empty butane cylinder, as Juan Antonio Madrid Mendoza , director of the National Reference Center of Cartagena FP, explained to El Pais. "We didn't weigh it because we do not have scales in that range", he added. What they have done at the Center is to measure it. It has a circumference of 205 centimeters and a diameter of approximately 65 centimeters. "Obviously it's no longer a perfect sphere since it deformed when it hit the earth, so we can say that it's more an ellipsoid than a sphere,” continued Madrid Mendoza, referring to the first piece found, which, he explained, is the one he knows best because he took measures to protect it and avoid damage.
The key information is the measured circumference of 205 cm, which yields a diameter of 65 cm.

On Nov 19, La Universidad Politécnica de Cartagena (UPCT) reported the results of tests on the third sphere, that revealed a circumference of 200 cm and diameter 70 cm. Those values are inconsistent. Since circumference can be measured directly, it is likely to be correct, in which case the diameter is about 64 cm - close to that reported for the first sphere.

A Dec 26 article in La Gran Época, quoted Juan Antonio Madrid, Director of El Centro de Referencia Nacional de Formación Profesional de Cartagena, who stated that each sphere weighs about 23 kg, and is about 65 cm in diameter. This is the source of the values in Table 1.

If you have more accurate or complete information on physical properties or precise debris co-ordinates, please contact me.

Photos of the suspected debris and information on their discovery is in Appendix A.

The following section explains how the fireball and debris evidence led to the identification of the prime re-entry suspect.

3. Prime suspect is re-entry of 2008-010B

None of the objects officially reported to have decayed on or near Nov 3 were in orbits that could have matched the time of the fireball sightings and the locations of the debris. They were also too small to account for the size and mass of the debris. It quickly became clear that the debris and fireball sightings would be key to solving the case.

3.1 Debris locations reveal approximate orbital inclination

Re-entry debris that survives to reach the surface of the Earth falls into a long, narrow zone commonly called the debris footprint, that closely parallels the ground track of the parent object. Typically, the footprints are hundreds of kilometres long, but only about 30 km wide. The densest debris falls well within about 10 km to either side of the ground track. How far, and on which side, depends on the wind speed and direction, and the ballistic coefficient of the debris. The narrowness of footprints compared to their length is a useful property, that enables the trajectory of objects that have re-entered to be deduced from the locations of their debris on the ground.

Figure 2 (below) shows the approximate locations where debris was discovered, and the implied re-entry ground tracks.

[Approximate Debris Discovery Locations]
Fig. 2.  Debris locations reveal possible re-entry tracks

The red line passes within a few kilometres of four of the five pieces of debris. Its orientation is consistent with re-entry from an orbit inclined approximately 64 deg, travelling from northwest to southeast. The metal strip was found about 70 km from this line, which probably is too far for it to have been carried there by the upper atmosphere wind.

The blue line connects a different subset of four pieces of debris, that includes the metal strip. Its orientation is consistent with re-entry from an orbit inclined approximately 44 deg, travelling from west-southwest to east-northeast. The metal object found near Pozorrubio was about 200 km from this line, which is too far for it to have been carried there by the upper atmosphere wind.

Since the fireball was observed to be travelling substantially southward - "southeast-east," according to Sr. Ruiz Gomez in Almería, the red line seems the more likely of the two. Therefore, the object that re-entered, probably was in approximately a 64 deg inclination, that would have been coplanar with the debris locations on 2015 Nov 03 at about 06:00 UTC, heading southeast. That is a very well constrained search orbit.

3.2 Search for objects in matching orbits that were near decay

The most likely possible explanations for the lack of any warning of the re-entry by USSTRATCOM, or acknowledgment after the fact, are as follows:

1. The object had been lost, perhaps never catalogued.

2. Orbital and re-entry data had been withheld, because the object was a military payload or associated rocket body.

A thorough check for large objects recently lost by USSTRATCOM, revealed no likely candidates for the re-entry in question. That left only the military satellite hypothesis. The approximately 64 deg inclination implied by the debris locations and fireball sightings, suggested an object in a Molniya orbit, which is highly elliptical, typically inclined between 62 and 64 deg. Independent sources were consulted to check this possibility.

The author is a member of a small, informal group of amateur astronomers, who specialize in tracking satellites in unpublished orbits. They share their observations and analyses of several hundred such objects via the SeeSat-L mailing list. On October 15, Scott Tilley observed a satellite that he could not immediately identify. Mike McCants identified it as a Centaur upper stage, which had the international designation 2008-010B, and the USSTRATCOM (U.S. Strategic Command) catalogue number 32707. It had last been knowingly observed in February, when it was far from decay. Mike fit an approximate orbit to Scott's observations, which revealed that by October the orbit was decaying rapidly.

This Centaur had flown on Atlas-V number AV-006, on March 13, 2008, from Vandenberg AFB, carrying the NROL-28 payload for the National Reconnaissance Office. The Centaur had been discarded in a Molniya orbit. Its rapidly decaying, 63 deg inclination orbit, made it a good fit to the description of the suspect sought in the investigation of the re-entry over Spain. The hobbyists did not observe 2008-010B after October 15. To learn its fate, the investigation turned to another independent source of orbital data.

Russia's International Space Observation Network (ISON) conducts scientific research into high altitude orbital debris. Its global network of telescopes has detected thousands of small debris fragments that are potentially hazardous to spacecraft. Cameras that can see faint debris, inevitably detect satellites and rocket bodies. ISON's data analysis partner, JSC Vimpel, distributes orbital data on 1,700 newly detected objects, via its web-based portal. The majority of those orbits are not found in USSTRATCOM's public database. The data had not been correlated with known objects; however, the author and his colleagues had previously identified a number of U.S. military objects of interest to them. One of them was a large object with the ISON identifier 68101, that the hobbyists knew was 2008-010B. ISON observed it frequently during 2015, and its data confirmed that by October it had been rapidly approaching decay. Figure 3 (below), shows the evolution of its altitude of perigee and apogee during 2015.

[Altitude history of 2008-010B]
Fig. 3.  Altitude history of 2008-010B.

At the start of 2015, 2008-010B was in a 63.4 deg orbit, with perigee of 276 km (blue data in Figure 3) and apogee of 38211 km (red data). Due to the high apogee, which extended one tenth the distance to the moon, the orbit was strongly perturbed by lunar, and to a lesser degree, solar gravity. As a result, the eccentricity slowly oscillated, causing the apogee and perigee to rise and fall. Eventually, the perturbations forced the perigee into the dense layers of the upper atmosphere, which greatly increased the rate of decay, causing the apogee to descend, while the perigee remained fairly constant.

Figure 3 shows the onset of rapid decay in early June, after the perigee descended below 150 km. The rate of descent was fairly constant until late September, by which time the apogee had been reduced by about 15,000 km. The perigee had remained fairly constant until that time, but now it began to descend further into the upper atmosphere, greatly increasing drag, which completed the destruction of the orbit in five weeks. As this is written, the latest known ISON observation was about Nov 1. ISON's extrapolated orbit for late Nov 2 (the final red data point in Figure 3), was just hours from re-entry.

On Nov 14, the author alerted his colleagues via SeeSat-L to the results of a quick analysis that showed a possible correlation between the re-entry of 2008-010B and the recent events in Spain.

Before proceeding with a detailed decay analysis, research was undertaken to determine whether any of the recovered debris matched known components of the Centaur in question.

3.3 Recovered spheres consistent with those of Atlas-V Centaur stage

The Centaur stage of the Atlas-V has undergone design changes since the first launch in 2002. The original version was called the Common Centaur, because it was used on the Atlas IIIB, as well as on Atlas-V. Jonathan McDowell's satellite catalogue lists the Atlas V in question as AV-006, which means that it was the sixth one built; therefore, it probably was the Common Centaur version. The United Launch Alliance (ULA) paper, The Centaur Upper Stage Vehicle, describes its pressurization system:

The tank pressurization system on the Common Centaur consists of three composite-wrapped 26-in. helium storage spheres connected to the propellant tanks through the new single pneumatics panel. Two of the helium bottle locations are common between the single- and dual-engine Common Centaurs, and the third is unique. A fourth helium bottle kit is available to support three-burn mission profiles.
The paper includes a photo of the Common Centaur, in which the three helium pressurant spheres are clearly visible:

[Common Centaur]
Fig. 4.  Source: ULA.

The Atlas Launch System Mission Planner’s Guide (CLSB-0409-1109), Revision 10, December 2004, provided a more detailed description of the Common Centaur's helium pressurization system on page A-12:

Helium Supply System — The baseline configuration for short-duration coast missions (<25 minutes) requires three 66.0-cm (26-in.) composite helium storage spheres charged to 27,580 kPa (4,000 psi). The spheres are graphite-overwrapped and reinforced with a 301 CRES metallic liner that provides leak-before-burst capability. A pressure regulator provides 3,450-kPa (450-psig) helium for engine and reaction control system controls. The three helium storage bottles provide ample helium for launch of direct ascent and first descending node geosynchronous transfer trajectory missions. This complement of bottles is used on all Atlas V GTO class missions. For longer coast duration missions, an additional helium bottle can be installed, as required.
This confirms that the spheres were COPV, and reveals that their diameter was 66 cm, close to the 65 cm measured diameter of the three spheres found (Section 2.2).

A fourth helium tank could be added for missions that required the Centaur to make manoeuvres later than about two hours after launch. Jonathan McDowell expressed confidence that this Centaur made only two burns; therefore, was the 3-tank version. The author's pre-launch analysis estimated that the second Centaur burn was expected about 43 min. after launch, well within the known capability of the standard 3-tank configuration.

The discovery in Spain of COPV spheres identical in number, size and construction to those of 2008-010B, strongly supported the circumstantial case that it was their source. The final test of this hypothesis was to verify its temporal and spatial correlation with the fireball sightings and the locations where the suspected debris was found.

4. Orbital decay analysis of 2008-010B

4.1 Satevo Decay Propagation Analysis

An object decaying over the region where the fireball was seen and the spheres fell, on Nov 3 at 06 UTC, from a 63 deg orbit, southeast-bound, would have had the following approximate theoretical orbital elements as it passed overhead, expressed in standard TLE (2-line element set) format:

1 70000U          15307.25000000  .00000000  00000-0  00000-0 0    03
2 70000  63.0000 334.0500 0000100   0.0000 136.0000 16.75000000    03
For 2008-010B to correlate with the re-entry, its orbit must have been expected to decay near Nov 3 at 06 UTC, and its right-ascension of ascending node at the time of decay, must have been close to that of the above theoretical orbit, about 334 deg.

Cees Bassa de-osculated the final three ISON orbital element sets to produce mean elements compliant with SGP4 (Simplified General Perturbations), shown below in TLE format.

1 99999U 14999A   15292.94709449  .11235444  00000-0  63774-3 0    09
2 99999  63.0275 352.1149 5452252 252.9231  55.6585  5.13054259    02

1 99999U 14999A   15299.96763898  .27393067  00000-0  78608-3 0    01
2 99999  63.0189 347.0289 4132690 253.2099  86.7297  7.51978834    03

1 99999U 14999A   15306.96370347 4.32729864  00000-0  18346-2 0    03
2 99999  62.9812 335.8047 0662118 262.1632 109.2725 15.11730730    05
The elements were propagated to decay using Alan Pickup's Satevo program. It is based on the published research of Dr. Desmond King-Hele, who was among the leading investigators into the mathematics and physics of Earth satellite orbits during the first three decades of the space age. Satevo quickly and reliably propagates any given TLE to decay, reports the estimated date and time, and generates propagated TLEs for each revolution up to decay. The results of the analysis are summarized below.

Table 2:  Results of Satevo Decay Propagation Analysis
Epoch Age Propagated Time of Decay Time To Decay Prediction Error RAAN at Decay
yyddd.dddd d yyddd.dddd mmm dd hh:mm d d % deg
15292.9471 1 15308.1526 Nov 4 03:40 15.206 +0.903 5.6 334.7
15299.9676 6 15306.2495 Nov 2 05:59 6.282 -1.000 -8.1 334.7
15306.9637 1 15307.0580 Nov 3 01:24 0.094 -0.192 -17.6 334.7

The propagated date of decay ranged between Nov 2 and Nov 4 UTC, close to the actual date of Nov 3 UTC. The rule of thumb decay prediction uncertainty is 20 percent of the time from the epoch of the elements to propagated decay. The absolute error ranged between approximately 6 and 18 percent. It should be noted that in calculating the error, the age of the underlying observations at the epoch of the elements (column 2) was added to the time to decay (col 5).

The RAAN (right-ascension of ascending node) at decay was estimated by adjusting the rate of decay to cause the time of decay to match the reported time of the fireball. In each case, the resulting RAAN was 334.7 deg, close to the theoretical value of 334 deg. The difference can be explained at least in part, by the imprecision with which the time of the fireball sightings and locations of the debris are known.

4.2 GMAT Propagation

A realistic re-entry trajectory has been computed using GMAT R2014a (General Mission Analysis Tool), "developed by a team of NASA, private industry, public, and private contributors."

The analysis was performed using GMAT's Dormand-Prince 78 numerical integrator, with a 90 degree, 90 order gravity field, and the MSISE90 atmosphere model, with space weather data entered manually. Orbital elements in TLE format were converted for GMAT propagation using TLE Analyzer 2.12.

The rate of decay is determined by the co-efficient of drag (Cd) and the area to mass ratio (A/m). The former was taken to be 2.2. A/m was estimated from the known physical properties of the Common Centaur, which was more than 12 m long overall, including the engine bell. Its main body was 3.05 m in diameter and about 9 m long. The combustion chamber and engine bell were significantly narrower. Its inert mass was 2,086 kg. The estimated average A/m is about 0.012 m2/kg.

Of the three ISON orbital element sets available, the one from Oct 19 has so far proven best to work with, probably because it had been extrapolated only one day beyond the latest observation to that point. The Oct 26 elements were based on 6 day old observations; therefore, they probably had some error due to the inevitable difference between the actual rate of decay and that of the elements. The Nov 2 elements were extrapolated one day beyond the latest observation, but since the object was close to decay, it is probable that there was considerable error due to the difference between actual and propagated rate of decay.

The analysis began with ISON's Oct 19 elements, de-osculated to an SGP4 TLE by Cees Bassa:

1 99999U 14999A   15292.94709449  .11235444  00000-0  63774-3 0    09
2 99999  63.0275 352.1149 5452252 252.9231  55.6585  5.13054259    02
Obtaining a realistic propagation of the Oct 19 elements over 14 days, for so difficult a class of decay, proved to be as challenging as expected. The result is extremely sensitive to the accuracy of the initial orbit, and the atmospheric model. For example, due to the ultra-low perigee height, the rate of decay was highly sensitive to small errors in the eccentricity, which are unavoidable. The approach taken was to make small adjustments in the eccentricity, by trial and error, that enabled propagation to decay close to the observed time of the fireball, using a reasonable value of A/m.

The analysis began with A/m = 0.012 m2/kg, and Cd = 2.2, which caused GMAT to propagate the orbit to decay far too early. Using an unrealistically low A/m yielded decay on Nov 3, but about one rev too early.

Of the many combinations of A/m and eccentricity tried, the best result was obtained with A/m about 0.006288 m2/kg, and an eccentricity that raised the perigee about 2 km over that of the reference orbit:

1 99999U 14999A   15292.94709451  .11235444  00000-0  63774-3 0    02
2 99999  63.0275 352.1149 5450405 252.9231  55.6585  5.13054259    00
The resulting GMAT script propagated the orbit to decay over Spain to within about 5 min. of the fireball sightings. The following TLEs are derived from the GMAT state vectors at the point of descent to 100 km and 62 km above the geoid, respectively (not all implementations of SGP4 may accept sub-orbital TLEs):
                                                          -6 X 116 km
1 70000U          15307.24350440  .00000000  00000-0  00000-0 0    08
2 70000  62.9550 334.4105 0095111 241.4349 233.9852 16.82137331    07
                                                        -3916 X 63 km
1 70000U          15307.24722230  .00000000  00000-0  00000-0 0    86
2 70000  62.4493 335.0440 4469413 312.4050 187.5337 29.20294201    07
Note the close agreement with the aforementioned 334 deg RAAN of the theoretical orbit, particularly at 100 km, prior to the strong drag perturbations experienced in the mesosphere. The trajectory passes the region of the fireball sightings and debris about 5 min. early and somewhat to the east.

The high altitude wind on the morning of the re-entry was predominantly from the SW; therefore, the debris probably fell on the east side of the ground track. Delaying the time of passage 340 s, and taking into account Earth's rotation, was sufficient to place the trajectory just west of the debris zone at about 06:01 UTC, in excellent agreement with the reported fireball sighting times.

Kml files suitable for use with Google Earth have been produced that display the adjusted descent trajectory from 100 km altitude to theoretical impact, at 5 s intervals. The 3D version represents the trajectory relative local terrain, for use with G.E. ground-level view. The 2D version represents the ground track as viewed from above the Earth (it avoids the parallax that results from viewing the 3D trajectory from overhead).

The following sub-sections compare the trajectory with the debris locations, observations of the fireball, and the image of the suspected smoke trail.

4.3 2008-010B correlates with debris locations

The estimated 2008-010B re-entry trajectory would have passed close to the locations where the suspected debris fell, and within visual range of all three places where fireball sightings were reported, shortly after 06:01 UTC (7:01 AM CET), moving from NW to SE, depicted by the line in Figure 5. The alternating red and white segments span 5 seconds of flight.

[Approximate re-entry track of 2008-010B]
Fig. 5.  Approximate re-entry track of 2008-010B relative debris locations.

The estimated ground track is remarkably similar to the hand-drawn theoretical one, depicted by the red line in Figure 2, that informed the investigation that lead to the identification of 2008-010B as the prime suspect.

The ground track is about 12 km SW of the flanged pipe or duct elbow found in Cuenca, and between 4 km and 7 km SW of the three spheres that fell in Murcia. It passed 7 km SW of the cylindrical tank found in March 2016 near Isso (Albacete).

The ground track passed 80 km SW of the 4 m long metal strip found in Alicante, which seems to be near the empirical limit of cross-track dispersion of re-entry debris. About 97 percent of the recovered debris of space shuttle Columbia was found within 5 NM (9 km) of its re-entry ground track. This consisted primarily of the lowest A/m objects. The remaining 3 percent was dispersed up to about 80 km from the ground track (CAIB final report, Appendix D.16). A study into the risk posed by re-entry debris to aircraft, assumed that the width of the airspace potentially including re-entry debris is 35 km on either side of the ground track. These facts call into question the relationship between the metal strip and the re-entry of 2008-010B. Expert analysis based on the object’s ballistic and aerodynamic properties, and local wind velocity would help resolve the question. Determining whether the object was a unique component of 2008-010B would be decisive.

4.4 2008-010B correlates with fireball sighting

From Almería, Sr. Ruiz Gomez briefly observed what he later realized must have been the re-entry fireball (report in Section 2.1.2). His view was mostly in the north and northeast. Figure 6 (below) depicts the estimated trajectory using the 3D kml file.

[Re-entry trajectory from Almería, facing azimuth 20 deg.]
Fig. 6.  Re-entry trajectory from Almería, facing azimuth 20 deg.

The alternating red and white segments represent 5 s of flight. In G.E., clicking on a segment displays the time and altitude above the Earth at the start of the segment.

Sr. Ruiz Gomez, has used the kml file to help reconstruct from memory the events of his brief fireball sighting. Below is an annotated illustration that he shared with me, followed by his description.

[Re-entry trajectory from Almería, facing azimuth 20 deg.]
Fig. 7.  Reconstruction of sighting from Almería. Courtesy R. Gomez.

Sr. Ruiz Gomez provided the following description of the events depicted in Figure 7 (English translation by Allen and Zaida Thomson).

Descripción de la fotografía:
Description of the photography:
Sobre los límites de tiempo y recorrido de la reentrada.
Concerning the timeline and path of the reentry
Para la fotografía me he basado en la órbita de Ted y en lo que recordaba del avistamiento. He de decir que al ver la órbita de Ted en Google Earth enseguida me recordó el inicio de la reentrada. Que la representación de la reentrada se iniciase por el mismo lugar y con la misma orientación que me había parecido ver me ayudó mucho a recordar y a confirmar que ése era el evento que había visto.
For the photography, I've used Ted's orbit and what I remembered about the sighting. I have to say that on seeing Ted's orbit in Google Earth I immediately remembered the beginning of the reentry. That the depiction of the reentry began at the same place and with the same orientation that I thought I saw did a lot to help me remember and confirm that that was the event I had seen.
En principio indiqué que había visto unos 30 segundos de reentrada, pero luego pensé que tal vez entre que me percato de ello, el asombro de un primer momento, sacar la cámara y disparar, habrían pasado unos cuantos segundos. Los 30, que realmente suelen ser 33 o 34 segundos (captura imagen, procesar imagen y estar de nuevo disponible para 16 segundos de exposición), teniendo en cuenta lo anterior se harían más largos. Por eso, en esa representación he considerado hasta 45 posibles segundos (entre 06:00:10 y 06:0055); ademäs de esa manera, la diferencia de azimut entre principio y fin es algo mayor y más próximo a la zona en la que creo que terminó. No obstante, he añadido un error de +/-5 segundos para indicar que la reentrada pudo terminar un poco más al oeste (5 segundos menos) o al este (5 segundos más).
At first I noted that I had seen about 30 seconds of the reentry, but then I thought that perhaps between the time I saw it, my astonishment at that first instant, and the time it took to get the camera and shoot the picture, several seconds had passed. The 30 seconds, which really were probably 33 or 34 seconds (capture the image, process the image, and then be ready again for 16 seconds of exposure), keeping this in mind, would mean more time. For this reason, in that depiction I have thought it might even have been 45 seconds (between 06:00:10 and 06:00:55). Also, if that were the case, the azimuth difference between the beginning and the end would be somewhat higher and closer to the place of depiction where I think it was found. Nevertheless, I have added a margin of error of +/- 5 seconds to indicate that the reentry could have ended a bit more to the west (5 seconds less) or the the east (5 seconds more).
Si la reentrada terminó 5 segundos antes, o sea, un poco más al oeste, entonces coincidiría con la entrada en la penumbra a los 06:00:50, y si fue 5 segundos después habría entrado a plena luz del Sol. No estoy muy seguro del lugar exacto, pero sí que tras esa última explosión, algo pareció intentar continuar, además como si ganase más impulso tras la explosión, pero se perdió rápidamente de vista (entre la explosión y el momento en el que pierdo de vista al objeto impulsado por la explosión no creo que pasaran más de 3 segundos, sino menos).Como se puede ver en la representación, especialmente ese momento de la explosión, he distinguido cómo salía ese último objeto, primero con un color anaranjado bastante claro, y después lo he continuado con un color gris claro que casi se confunde con el cielo para indicar que por un momento se pudo ver cómo salía despedido ese objeto tras perder ese color anaranjado muy claro. Tal vez, esa repentina pérdida de visión de la reentrada pueda servir para situar mejor el evento de la pérdida de visión de la reentrada.
If the reentry ended 5 seconds before – in other words, a bit more to the west – then it would coincide with the entry in the shadow at 06:00:50. If it was 5 seconds later, it would have entered in full sunlight. I'm not very sure of the exact place, but I am sure that following that last explosion, something seemed to try to continue, as if it had gained more momentum following the explosion, but it quickly went out of sight. I don't think more than 3 seconds – perhaps less – passed between the time of the explosion and the time at which I lost sight of the object expelled by the explosion. As can be seen in the depiction, especially when the explosion happened, I have shown how the object was expelled initially by drawing it in a light orange color, and then I used a light gray color almost the same color as the sky to show that, for a moment, one could see how the object was expelled after losing that very light orange color. Perhaps that sudden loss of the sighting of the reentry may help to better locate the loss of the sighting of the reentry.
Descripción cronológica.
Chronological description.
Antes de empezar este apartado, señalar que aunque en la representación he distinguido 3 fases con el mismo tiempo, en la realidad puede no haber sido así. Es posible que la primera fase durase algo más que las otras dos, más rápidas, pero fuese como fuese, sí puedo distinguir entre esas 3 fases, especialmente entre las dos últimas.
Before beginning this section, I would point out that although in the diagram I have shown the three phases as having the same duration, it may not actually have been that way. It's possible that the first phase lasted slightly more than the other two, which may have been shorter. However, regardless of how long they were, I was able distinguish among these three phases, and especially between the last two.
Yo estaba muy cerca de la puerta de salida de la azotea. Esa pared mira aproximadamente al E, lo cual no ayudaba mucho, pero desde donde me encontraba tenía el ángulo justo para ver hacia el NW. La reentrada estaba muy baja, apenas un poco por encima de las montañas de Sierra de Gádor, era de un color anaranjado bastante oscuro y fácil de distinguir contra el cielo más claro, aunque al ser por el W, no estaba tan claro como la parte de cielo orientada al E. No obstante, se podía distinguir perfectamente.
I was very close the exit of the roof terrace. That wall faces mostly east, which did not help much, but I was at exactly the right angle to see toward the northwest. The reentry was very low, barely above the mountains of the Sierra de Gador. It was a fairly dark orange color and easy to see against the lighter sky, although being to the west, it was not as clear as the area of the sky toward the east. Nevertheless, it was possible to see it clearly.
Tras ese primer momento, saqué la cámara, apunté y disparé, pero ello me llevaría unos segundos. No obstante he de aclarar que en ese momento ni tan siquiera era consciente de que hubiese disparado. Es ahí, o al poco, cuando me parece que el principal objeto de la reentrada se rompe en varios más finos que siguen su camino un poco más arriba y con un cierto recorrido. También indicar que conforme el objeto principal de la reentrada iba ascendiendo, su color anaranjado se iba aclarando poco a poco. Tampoco puedo precisar si hubo un sólo punto o varios en los que ocurriese esto; pero esa primera fase se caracteriza por ese tipo de hechos. Aunque en la representación aparecen 2 posibles piezas de rotura de la principal, en la realidad es posible que fuesen unas cuantas más.
After that first instance, I took out the camera, aimed, and shot, but that took me a few seconds. Nevertheless, I should clarify that at that moment, I was not even aware that I had shot the picture. It was then, or shortly thereafter, that I thought that the principal reentry object broke up into smaller pieces which followed its path a bit higher up for a distance neither short nor long. I will also note that as the principal reentry object was ascending, its orange color was slowly getting lighter. I cannot say whether this happened once or several times, but that is what happened during this first phase. Although the drawing shows two pieces breaking off from the main piece, there may actually have been several other pieces.
Una segunda fase bastante clara fue la rotura de la pieza principal en numerosas piezas más pequeñas que realizaron un recorrido bastante corto antes de perderse de vista. Por un momento, pensé que ahí terminaría, pero el objeto incandescente principal continuó con algo más de velocidad. Poco después de ello, y pensando que no había pulsado el obturador de la cámara miré al LCD y vi que estaba procesando, así que inmediatamente continué a simple vista la reentrada (eso quiere decir que poco después de ese evento quedaría un máximo de 16 segundos hasta el final, pero no puedo especificar el mínimo que podría ser bastante menor. Al fin y al cabo, de media, cada fase tendría unos 15 segundos). También indicar que mientras avanzaba, el color anaranjado del objeto principal de reentrada seguía aclarándose, y que cuando se rompió en esas numerosas piezas de corto recorrido, el color anaranjado de todas ellas y del objeto principal parecía más vistoso (ni tan oscuro como al principio, ni tan claro como al final).
A second fairly distinct phase was the breakup of the principal piece into many smaller pieces which had a fairly short trajectory before they were out of sight. I thought for a moment that that would be the end of it, but the primary burning object kept going at a slightly faster speed. A little after that, and thinking that I hadn't pressed the shutter button of the camera, I looked at the LCD and saw that it was processing, so I immediately continued simply watching the reentry (this means that a little after that event there remained a maximum of 16 seconds until the end, but I can't specify the minimum, which could be significantly less. At the end of the day, on average, each phase would have lasted about 15 seconds.) I should also note that while it moved along the orange color of the principal reentry object continued to get lighter, and when it broke up in those numerous pieces that traveled only a short distance the orange color of all of them and of the principal object seemed more intense (not as dark as the principal object, nor so light as at the end).
Tras esa última separación de piezas del objeto principal, éste último continuó su camino, más rápido y aclarándose el color anaranjado que tenía rápidamente hasta el punto de que empezaba a resultar algo difícil distinguirlo del cielo. Continuó así, hasta que explotó. Esa explosión parecía como en zig-zag de un color anaranjado bastante claro, casi amarillo, pero tampoco muy lejos de confundirse con el cielo, y terminó como ya he señalado, impulsando un último objeto que rápidamente perdí de vista. Tras eso, no pude ver nada más, miré rápidamente a la cámara y a los 2 o 3 segundos ya había terminado de procesar y estaba disponible. Luego, volví a mirar hacia la zona del cielo donde había terminado la reentrada y me quedé en blanco. Tal vez el hecho de no haber obtenido una buena fotografía de la reentrada me impulsó a quedarme y a descubrir poco después el posible humo consecuencia de la reentrada.
After that last separation of pieces from the principal object, this latter continued on its path, more quickly and quickly becoming a lighter orange color up to the point it became somewhat difficult to distinguish it in the sky. It continued that way until it exploded. That explosion looked like a zig-zag of fairly light orange color, almost yellow, but not very far from fading into the sky and it ended like I already said, expelling a last object which I quickly lost sight of. After that, I couldn't see anything else. I quickly looked at the camera and within 2 or 3 seconds it had finished processing and was usable. Then I again looked at the area of the sky where the reentry had ended and my mind went blank. Perhaps the fact that I had not gotten a good photograph of the reentry prompted me to stay and shortly thereafter to find smoke that possibly resulted from the reentry.

4.5 Analysis of image of suspected smoke trail

From Almería, Sr. Ruiz Gomez photographed what appeared to have been a short smoke trail, that lingered in the bright morning twilight. The lack of a photograph from another location, precluded the use of triangulation to determine the geographic location of the trail. However, the hypothesis that it was a remnant of the re-entry could be tested by projecting its altitude along a line from the co-ordinates of the observer, through the topocentric co-ordinates of the trail, with minimum altitude constrained by the requirement for solar illumination. This revealed that it was far higher in altitude than the maximum of clouds or aircraft contrails, and that if it was over the re-entry ground track, then it was near the altitude of peak heating, where a smoke trail could easily have formed.

Sr. Ruiz Gomez enabled the analysis, by measuring the azimuth and elevation of the trail. For confidence, he used two independent methods. The first made use of known terrestrial features (distant mountains) to calibrate the image, which yielded azimuth 26.2 deg and elevation 14.68 deg for the left edge of the trail. The second method superimposed a photograph of stars taken with the same camera and settings, shown in Figure 8 (below):

[Composite of suspected smoke trail and proximate stars]
Fig. 8.  Composite of suspected smoke trail and proximate stars. Courtesy R. Gomez.

Sr. Ruiz Gomez photographed the superimposed stars on 2015 Nov 27 at 06:12:20 UTC. He found that kappa Cygni (azimuth 26.25 deg) was close to the azimuth of the faint, left edge of the trail, which he took to be 26.2 deg. Using 45 and 54 Draconis, he obtained an elevation of 14.7 deg near the left end. These results agree closely with those of the first method. The author used 45, 46, 47 and 48 (Omicron) Draconis, to estimate the position of the middle of the trail: azimuth 27.7 deg, elevation 14.9 deg.

Projecting from the observer's co-ordinates (36.83922 N, 2.44964 W, 30 m AMSL), through the azimuth of the trail, intersects the estimated re-entry ground track near 38.09 N, 1.62 W. Given the elevation of the trail, its altitude must have been about 44 km. That is far higher than the typical maximum height of cirrus clouds (14 km), or aircraft contrails (13 km). Slant range from the observer would have been about 163 km.

The trail would have entered the penumbra about 06:04 UTC, and full sunlight about 06:07 UTC. The time of the photo was 06:10:45 UTC +/- 1 s; therefore, it would have been illuminated, but not far from the penumbra.

The close proximity to the penumbra suggested a method of testing whether the trail could have been a cloud or aircraft contrail. Table 3 reveals that for its mid-point to have been within the penumbral boundaries at the observed time and topocentric co-ordinates, its altitude must have been between about 29.9 km and 35.5 km. That is far higher than the typical maximum height of cirrus clouds or aircraft contrails, which tends to confirm that it was a remnant of the re-entry fireball. A meteor could conceivably have left the trail, but this seems an unlikely coincidence.

Table 3:  Trail Position at Penumbral Boundaries
Latitude
Longitude
Altitude
Boundary
deg N
deg W
km
Penumbra-umbra
37.693
1.885
29.9
Sunlight-penumbra
37.847
1.781
35.5

Since the photo was taken about 9 min. after the estimated time of passage of the re-entry fireball, the position and shape of the smoke trail would have been affected by the upper atmosphere wind. According to one model, at the time of the fireball and the estimated location of the trail, the wind at 10 hPa (roughly 30 km), was 60 km/h, from azimuth 280 deg. If this was true at 44 km, then the trail would have drifted east about 9 km. Allowing for this difference would increase the estimated altitude of the trail by about 0.65 km, which is within the margin of error of the analysis, and in any case would tend to support the finding that it was much higher than clouds or aircraft contrails.

Assuming the smoke trail formed above the re-entry ground track, then it was 44 km above the region where the three COPV spheres fell. This was near the altitude of maximum re-entry deceleration, about 7 g, where peak heating occurs. The attendant rapid disintegration could have produced the particulate matter to form a trail. Large fragments of debris in its vicinity might have produced sonic booms audible from the ground. Recall from Section 2.1.1, the witnesses in Las Cumbres, less than 10 km north of where the first sphere was found, who heard a "roar like thunder" (estruendo), after they lost sight of the fireball.

5. Conclusions

Virtually all identifications of suspected sightings of re-entry fireballs and debris recoveries are circumstantial. Authoritative records of known re-entries are consulted to identify potential suspects. Their final orbital elements before re-entry reveal whether they happened to be passing within range of the sightings or close to the location of any debris at the relevant time, and whether they might have descended low enough to have been burning and breaking up. Even with accurate orbital data, it is seldom possible to precisely estimate the time and place of the final descent. Confidence in the circumstantial case depends on the quantity and quality of the sighting and debris reports, and the strength of correlation with the trajectory.

Bright twilight reduced the Spanish fireball of November 3, 2015 to a fraction of its normal brilliance. Had it occurred half an hour earlier, there would have been hundreds of sightings and numerous cell phone videos on YouTube. Fortunately, the known sightings agreed closely on what appears to be the correct approximate time of the event, and the substantially southbound trajectory.

The locations of the recovered debris provided by far the strongest evidence of the orbital inclination.

The time, place, inclination and direction of travel of the re-entry fireball defined a very well constrained search orbit, that enabled easy detection of the 2008-010B Centaur as the prime suspect, among the respective orbital data of the hobbyists and ISON.

The three spheres found near Calasparra matched the number, size and construction of the helium pressurant spheres carried by the Centaur stage. The cylindrical tank found four months later near Isso, matches its hydrazine tank.

Additional information is sought, that could further test the circumstantial case, including:

  • authoritative physical data on each piece of suspected debris
  • the precise location of discovery of each piece of suspected debris
  • additional fireball sighting reports
  • Section 3.3 reported that the Centaur's helium spheres had a metal liner made of 301 CRES (Corrosion Resistant Steel). Metallurgical tests to confirm this would further test the 2008-010B hypothesis. If the flanged pipe or duct elbow found near Pozorrubio de Santiago is confirmed to have come from 2008-010B, then it will help to better define the actual debris footprint, and may help experts to verify existing re-entry debris survival analyses of the Common Centaur.

    If you have information, please contact me.

    5.1 What's next for the debris?

    If history repeats, then despite the air of secrecy surrounding the re-entry, the U.S. will eventually repatriate its debris.

    On 2010 Feb 19, near 03:32 UTC, pieces of the second stage of the Delta II rocket that launched the USAF's STSS Demo 1 and 2 satellites (2009-052C / 35939), landed in Mongolia. This object was from a military mission, so its orbit was secret, but Russell Eberst discovered it on 2009 Nov 23 UTC, a couple of months after launch. Hobbyists successfully tracked it to within hours of re-entry, resulting in the sole public history of precise orbital information on this object. USSTRATCOM had not issued any decay predictions, but it took less than a week for the precise source of the recovered debris to be reported by the Mongol News. How this came to be known in Mongolia is unknown. The Research Center Astronomy and Geophysics (RCAG) of the Mongolian Academy of Sciences later contacted the author of the present report, and provided the coordinates of the fall: 105:07:38.3 E (105.12731) 47:10:57.1 N (47.18253), and photographs of the propellant tank and the titanium pressure sphere. Pre-reentry observations were provided in return.

    In August 2011, the USAF openly sent a 15 person crew to Mongolia to retrieve the debris that had fallen there. The article does not identify the precise source of the debris, but a photo gallery on the recovery operation includes a photo of the actual launch. Yet, to this day USSTRATCOM has not acknowledged that this object has decayed from orbit.

    6. Acknowledgments

    Vicente-Juan Ballester Olmos was among the first to inform me of this case, and he has spared no effort in pursuing and analyzing the evidence. Among his many contributions are the co-ordinates of the reported places where debris was found, most of which are not known to Google Earth.

    Cees Bassa de-osculated ISON's orbital elements to produce SGP4-compliant 2-line elements sets.

    José Luis Ruiz Gomez reduced the topocentric co-ordinates of the smoke trail that he photographed, and calibrated his camera's clock to accurately determine the time it was taken.

    The International Space Observation Network (ISON), via its partner JSC Vimpel, provided the orbital data on 2008-010B, without which the case could not have been solved.

    Marco Langbroek brought to my attention the fireball sighting of Sr. Ruiz Gomez, located upper altitude wind data from Murcia, and provided helpful advice.

    Jonathan McDowell's satellite catalogue and launch history table were indispensable.

    Jon Mikel assisted in the effort to contact authoritative sources of information on the debris.

    Allen and Zaida Thomson provided the English translation of the Spanish text that appears in this report.

    Appendix A: Photos of Suspected Debris

    This section presents photos of the suspected re-entry debris, and information regarding their discovery. It supplements the technical information in Section 2.2, that was used to identify 2008-010B as the object that re-entered.

    A.1 COPV Sphere 1

    On Tuesday, November 3, 2015, brothers Francisco and Juan Espín del Amo found the first sphere, on their farm in Murcia. The location is Llanos del Cagitan, which is within the municipal boundaries of Mula, close to neighbouring Calasparra. The discoverers quickly shot 25 s of cell phone video, and sent it to their close friend, Iván Moya Sánchez. He searched the web, and soon discovered that it was similar to COPV helium pressurant tanks known to have re-entered from space in the past. At 2:36 PM, he posted his findings to Facebook. El Mundo reported the story and video.

    [COPV Sphere 1.]
    Fig. A1.  COPV Sphere 1. Source: Guardia Civil.

    A.2 Object found near Pozorrubio de Santiago

    On Saturday, November 7, 2015, a large object was found by a farmer in Monte Bajo, about 3.5 km from Pozorrubio de Santiago (Cuenca). The following photographs depict what appears to be a pipe or duct elbow, with an irregular break on one end, and a flange on the other. The news media reported its mass as 20 kg. Its size has been reported as 3 m, but scaling from the cigarette pack in Figure A.3, reveals a pipe diameter of about 40 cm. The largest dimension appears to be less than 1 m.

    The object was found approximately 12 km NE of the estimated re-entry ground track of 2008-010B, which strongly suggests that it is related; however, correlation is not necessarily causation. If it can be matched to a known feature of the Common Centaur, that would prove the relationship. If it is found to be made of a material that is known to survive re-entry, with signs of exposure to high temperature, then that, together with the proximity to the re-entry ground track, will also tend to prove a relationship. The resolution of the photos is insufficient for the author to confidently discern signs of melting.

    [Photo 1 of object found near Pozorrubio de Santiago.]
    Fig. A2.  Photo 1 of object found near Pozorrubio de Santiago. Source: Voces de Cuenca.

    [Photo 2 of object found near Pozorrubio de Santiago.]
    Fig. A3.  Photo 2 of object found near Pozorrubio de Santiago. Source: Voces de Cuenca.

    [Photo 3 of object found near Pozorrubio de Santiago.]
    Fig. A4.  Photo 3 of object found near Pozorrubio de Santiago. Source: Voces de Cuenca.

    A.3 COPV Sphere 2

    The second COPV sphere was found in the afternoon of Sunday, November 8, 2015, by Sr. Diego E. Rueda, on his farm in Villa Vieja, which borders the town of Calasparra. Below are photos of the sphere and the impression it made when it bounced before coming to rest.

    [COPV Sphere 2. Source: Television Calasparra.]
    Fig. A5.  COPV Sphere 2. Source: Assombrado.com.br.

    A.4 Metal strip

    A metal strip was found on Tuesday, November 10, 2015, in Las Barrancadas, near Elda (Alicante). The news media reported that it is 4 m long and 20 cm wide, and had been deformed by calcination (heating to a temperature below the melting point). Its thickness, mass and material(s) of construction have yet to be reported. The results of any expert examination for signs of re-entry heating are unknown.

    Since the location was below the air traffic route of a nearby airport, initial speculation was that it had fallen from an aircraft. Speculation quickly turned to a relationship with the then unknown re-entering object believed to have deposited the spheres in Murcia, and the flanged pipe or duct elbow in Cuenca. The discovery that the re-entry of 2008-010B correlates with those four objects, makes this highly unlikely, because the metal strip is too far from the re-entry ground track (Section 4.3).

    [COPV Sphere 2. Source: Television Calasparra.]
    Fig. A6.  Metal strip. Source: La Opinión de Murcia.

    A.5 COPV Sphere 3

    The third COPV sphere was found on Sunday, November 15, 2015, in Sierra del Molino, in Calasparra (Murcia), in the same general area as the first two spheres.

    [COPV Sphere 3. Source: Calasparra.org.]
    Fig. A7.  COPV Sphere 3. Source: Calasparra.org.

    A.6 Cylindrical COPV tank

    A cylindrical COPV tank with a titanium liner was found by Rafael Fernández and José Manuel, on Tuesday, March 8, 2016, near Isso, in Hellín (Albacete). According to some reports, the more precise location was El Pocico, predominantly agricultural land, which appears to be centred near 38.46 N, 1.83 W. One report stated it was El Pico, which appears to be an adjacent area, about 1.5 km east. The tank was described in news reports as 80 cm diameter, mass 10 kg, with a wall thickness of 1 mm. It appears to be an Atlas V Centaur hydrazine tank, which is the ATK model 80427-1, described as follows:
    The ATLAS V Hydrazine tank is a 23.25-in dia. X 33.85-in long pressure vessel constructed of annealed 6AL-4V Titanium and T-1000G graphite hoop wrap. The tank has 2 spun domes, with an integral 7.35 in long center cylinder section as part of the propellant dome. Positive propellant expulsion is provided by an AF-E-332 rubber diaphragm retained within the cylinder. Mounting is accomplished by 3 tabs bonded to the graphite wrapped cylinder and reinforced with a hoop wrap. Connection is made to the propellant and pressurant domes through tube stubs at each pole.
    Summary of the key design values:

    - diameter 59 cm (23.25 in.), length 86 cm (33.85 in.)
    - empty mass 19 kg (42 lbs)
    - minimum wall thickness 1 mm (0.04 in.)
    - propellant capacity 153 kg (337 lbs)

    The United Launch Alliance (ULA) paper, The Centaur Upper Stage Vehicle, reported that this tank was introduced with the Common Centaur, and that its first use on Atlas V was on vehicle AV002. The 2008-010B Centaur was AV006; therefore, it carried the same tank. Its capacity was considered sufficient for all known missions; therefore, only one tank would have been carried.

    Below is a photograph of a completed tank:

    [Atlas-V hydrazine tank. Source: ATK.]
    Fig. A8.  Atlas-V Centaur hydrazine tank. Source: ATK.

    Below are five photos of the recovered tank:

    [Photo 1 of cylindrical tank found near Isso. Source: Television Hellín.]
    Fig. A9.  Photo 1 of cylindrical tank found near Isso. Source: Television Hellín.

    [Photo 2 of cylindrical tank found near Isso. Source: Television Hellín.]
    Fig. A10.  Photo 2 of cylindrical tank found near Isso. Source: Television Hellín.

    [Photo 3 of cylindrical tank found near Isso. Source: Television Hellín.]
    Fig. A11.  Photo 3 of cylindrical tank found near Isso. Source: Television Hellín.

    [Photo 4 of cylindrical tank found near Isso. Source: Television Hellín.]
    Fig. A12.  Photo 4 of cylindrical tank found near Isso. Source: Television Hellín.

    [Photo 5 of cylindrical tank found near Isso. Source: Television Hellín.]
    Fig. A13.  Photo 5 of cylindrical tank found near Isso. Source: Television Hellín.

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