compiled from SeeSat-L by Bart De Pontieu
The article below is a compilation of many messages on SeeSat-L during the month of June.
Interesting news in the AWST that just landed in the mailbox:
Aviation Week and Space Technology
June 24, 1996, p.17
The U.S. Naval Research Lab deployed a 118-lb. (53 kg) experimental tether satellite in a circular orbit at an altitude of 1,022 km (552 naut. mi.) and inclination of 63.4 deg. The Tether Physics and Survivability TiPS) spacecraft consists of two small end-masses connected by a 4-km (2.5-mi.) nonconductive braided tether. The satellite was carried into space this spring with a classified payload that was launched on a Titan 4 booster. TiPS was then jettisoned from its "host vehicle on June 20, the NRL said. In an unprecedented move, the National Reconnaissance Office (NRO), which produces and operates U.S. intelligence satellites, said it provided funding for TiPS' launch and operation, contributing roughly half of the funding for the 2.1 million dollar project.
This tethered object, presumably tossed from the "A" object of the recent NOSS 2-3 launch, should be an interesting object for the amateur satellite watchers' community to try to find. Those equipped for video should try to get pictures.
P.S.: It would be interesting to know whether the "survivability" part of TiPS refers to the tether or the satellite as a whole, and what threat it is supposed to survive.
This is a partially classified Naval Research Laboratory project. A paper was presented last summer at the Utah State Small Satellite annual conference.
The survivability is indeed survivability of the tether - from meteoroid or debris damage. I believe the tether is identical to the SEDS tether (see my photo on the TSS viewer's home page) - it's made by the same company.
The two end-masses are nicknamed "Ralph" and "Norton" - with Ralph being the larger of the two (characters from the classic "Honeymooners" TV series staring Jackie Gleason and Art Carney).
From what I was led to believe the elements for the TiPS pair would be unclassified, and somebody at Goddard is supposed to be setting up a web page with sighting opportunities.
It's anticipated that it will not be as visually exciting as the SEDS tether due to the much higher altitude.
TETHER PHYSICS AND SURVIVABILITY EXPERIMENT (TiPS)
A. Peltzer, W. Purdy, and S. Coffey/NRL
The Tether (i) Physics and Survivability (TiPS) experiment is intended to be the first long term tethered satellite flight experiment. Two end bodies, weighing 90 and 20 pounds respectively, will be connected by a four kilometer long tether. The system will be placed in a 550 nautical mile circular orbit with an inclination of 63.40ree;. The tethered system will be jettisoned from a host spacecraft. The tether will be deployed after a period of separation from the host spacecraft. The TiPS experiment is presently planned to be operational in the spring of 1996.
There are two primary objectives to the TiPS experiment:
1. Evaluate the long term gravity gradient dynamics of a tethered system. 2. Gather data on the survivability of the tether in the space environment.
No tether experiment to date has been on orbit longer than about one month. As such, there is relatively little data on the long term dynamics of these systems. The dynamics of particular interest include in-plane and out of plane libration, system damping, orbital perturbations and environmental effects. The TiPS experiment is the first designed to maximize the survivability of the tether. The tether is predicted to have a mean life of 5 years before it is cut by orbital debris. The observed life of TiPS will help understand and validate these theoretical predictions.
The TiPS experiment will have its dynamics measured by Satellite Laser Ranging (SLR) and ground based radars. The SLR will provide very accurate measurements of the positions of each end body. The length and libration angles of the system will be determined repeatedly over a long period of time from these measurements. Analysis of this data will be compared to theory to improve the understanding of tether dynamics. The SLR data will be available over Internet. Each end body will be covered with 18 uniformly spaced laser retroreflectors to enable the ground based laser ranging. The retroreflectors on one body will be coated to reflect light from 420 nm to 850 nm. The retroreflectors on the other body will be uncoated. These two types of retros will enable differentiation between the two end bodies. The laser ranging operations are planned to last for a period of at least 6 months after TiPS deployment. The U.S. Space Command network of radars will be utilized to support the laser ranging and to provide continuing observation of the system for the duration of the TiPS lifetime to determine if or when the tether has been cut.
I observed the TiPS tether Saturday June 22 pre-sunrise at 1012UT from Houston, Texas USA. Passes on Sunday and today were rained out. The tether was about +6.5 magnitude in the northnorthwest (elevation 31 degrees), range 1721 km. It was about 0.12 degrees long. As it climbed to an elevation of 89 degrees, range of 1026 km, it lengthened only to 0.17 degrees and brightened to +5.5 at best. The phase angle varied between 90 and 73 degrees during the observing window. Three minutes of video was obtained and will be shown at EUROSOM 2.
Here is an element set that should be used for TiPS. The parameters are in their usual positions with unneeded ones omitted.
TiPS 3.5 0.0 0.0 5.7 1 96290U 96029 ? 96173.00694444 -.00000003 00000-0 -37763-5 0 08 2 96290 63.4290 169.7913 0003344 241.5909 128.6259 13.63734634 05
I have reviewed my video of the June 22 TiPS pass on a large monitor today. There are clearly visible episodic single flashes from the trailing (bottom?) end mass that reach about a magnitude above that of the tether itself. I estimate the flashes, from the video, at perhaps +4.0 magnitude. There are no similar flashes from the opposing end mass. The tether appears quite linear without variation in brightness from one end to the other. As the satellite passes overhead, the length does foreshorten, but unlike SEDS and TSS, this tether does not show any obvious bends.
I have noticed that TiPS may be very near 27:2 resonance - its groundtrack nearly repeats every 27 revs, or about every 2 days. Based on my search elset, the resonance is 27.0068:2; based on Rainer's, it is 26.9963:2.
On page 196 of a A Tapestry of Orbits, Desmond King-Hele states that the first satellite analysed at 27:2 was the Aureole 2 rocket, but severe drag limited the value of the results.
Perhaps the tether will in some way limit the usefulness of this object for geoid studies.
Don't know if a single data point will help anyone, but I spotted TiPS over Calgary, Alberta, this morning just about bang on time using the elset dated 96173.00694444. This point is very near to Mizar and Alcor in Ursa Major.
J2000.0 RA 13h 23.7m Dec 54d 58m at 9hrs 07min 27.3sec GMT Lat/Long/Elev 51.03997N 114.07767W 3450ft elev
Using 7x50 binocs I noticed no flashing, just two closely spaced objects in a line oriented exactly in their direction of motion. Objects looked 7th mag to me. Will use 11x80 binocs next time.
I observed the TiPS tether June 27 22:02:29.65 UTC about 0.1 deg above kappa Cas with 10x50B. The sky was rather bright (Sun 10.9 deg below my horizon), limit. mag about 7.5, thether mag about 7, phase angle 111 deg, range 1510 km.
One rev later (Sun -12.7 deg, limit mag 8.5) the thether was unvisible with my 10x50B. TiPS was irreg. flashing with brightest flashes about mag 5. It passed in front of SAO 71273 at 23:52:43.00 UTC (RA 21:23:17.4, D 39d20'57" 2000.0). phase angle 75 deg, range 1150 km
Pierre Neirinck timed several flashes at 23:50 with FP = 6.73 +/- 0.2 sec.
elset from 3 observations June 26 09:07 to June 27 23:53
TiPS 1 96290U 96029 ? 96180.00000000 .00001293 00000-0 16271-2 0 03 2 96290 63.4153 151.2871 0003344 241.5665 261.0312 13.63752718 06
I've observed the TiPS satellite on four passes over Calgary and can offer the following comments and suggestions:
TiPS should become a very popular object to watch for its unusual and unique appearance and characteristics. If you like to observe unusual objects like Japan's EGP, you'll add TiPS to your list.
I have found that if you want to see the tether easily, go for passes where the illumination phase angle (sun-sat-observer) is LESS than 90 degrees. I have seen passes where the tether seems to glow it's so "bright" (5-6th mag). This occurred with phase angles in the <45 degree range.
If you want to see the flashes the ends or near ends of the satellite seem to exhibit, I've seen them best when the tether is subdued in appearance, and that seems to take place when the illumination phase angle is GREATER than 90 degrees.
The next problem I'm struggling with is the tether's orientation relative to its direction of movement across the sky. The first time I saw the object, the tether was oriented exactly with its direction of movement. This morning (Sat Jun 29), however, I could swear I saw the tether perpendicular to its direction of movement, and this orientation changed as it crossed the sky. This has got to be a perspective thing, but I can't convince myself of this completely. I'll just have to watch some more. I'd sure like to see other comments on this object.
Most of my observations have been with 11x80 binoculars.