R: RE: Phobos-Soil Project seeks observations of engine burns from South America

From: satrack@libero.it
Date: Fri Nov 04 2011 - 19:38:40 UTC

  • Next message: Brad Young: "BY C 110411"

    I have loaded the two TLEs that have been provided on the phobos project's 
    website 
    (before and after the first burn), in the online program. The system 
    automatically switches 
    from the first TLE to the second one at the burn time.
    
    Maybe it can be of help to observers who just want to try to see the 
    spacecraft.
    
    If my program could be of help anyhow please let me know; 
    Time permitting, I am willing to add code if necessary.
    
    Here the link for Phobos:
    
    http://tinyurl.com/VSFT-Phobos-TLEs
    
    Best Regards,
    Simone
    
    
    
    >----Messaggio originale----
    >Da: ssl3molcz@rogers.com
    >Data: 4-nov-2011 18.55
    >A: <seesat-l@satobs.org>
    >Ogg: RE: Phobos-Soil Project seeks observations of engine burns from South	
    America
    >
    >I offer the following suggestions for prospective observers of the engine 
    firings.
    >
    >1. Plume Brightness
    >
    >I have been in contact with the project on the matter of expected plume 
    brightness, and received the following guidance
    >(which I have somewhat summarized), attributed to a professional in rocket 
    engine development and test. Despite
    >estimated exhaust gas temperature of about 500-600 K, which results in low 
    gas brightness at visible wavelengths, a very
    >bright plume is observed, due to very hot carbon particles generated in the 
    engine chamber. It is predicted that it may
    >be possible to observe the plume by binoculars, perhaps the naked eye.
    >
    >The reality is that we cannot be certain how bright the plume will be. If I 
    were in a position to attempt to observe the
    >engine firings, I would prepare for the worst case (a faint plume), and allow 
    myself to be pleasantly surprised if it
    >proves visible to the unaided eye. To enable precise astrometry of the 
    spacecraft's trajectory, which is the primary
    >objective, it will be required to observe a fairly faint star background, and 
    the optical equipment that will detect
    >such stars should do reasonably well on a faint engine plume.
    >
    >2. Observing Strategy
    >
    >When firing, the engine will be at the end of the spacecraft opposite the 
    direction of travel. This means that during
    >the first half of the pass, as the spacecraft approaches the observer, it 
    will block the observer's view of the engine,
    >and probably the brightest portion of the plume. After the point of closest 
    approach, as the spacecraft recedes, the
    >engine and brightest portion of the plume will be exposed to the observer, 
    maximizing visibility and apparent
    >brightness.
    >
    >So, if the plume proves faint, it will be more likely to be detected once the 
    spacecraft is somewhat east of the
    >observer. But that does not mean that observations should not be attempted 
    earlier in the pass. For trajectory analysis,
    >the longer the arc over which observations are available, the better; 
    therefore, I would plan to intercept the
    >spacecraft fairly early in the pass, but be prepared to rapidly re-aim to 
    intercept it at several later points. 
    >
    >In the event it is spotted at the earliest intercept point, then I would 
    track it as long as possible, and of course
    >record data. In the event that it is not seen at the first intercept point, 
    perhaps because it is faint, or obscured by
    >a passing cloud, I would move to the next intercept point.
    >
    >In selecting intercept points, I would verify that a reasonable number of 
    detectable stars will be in the field of view
    >(to aid in the astrometry), and I would make certain to allow sufficient time 
    between intercept points to re-aim the
    >optics. This last point is an important consideration for everyone, but 
    especially those closest to the ground track,
    >who will experience angular velocity well over 1 deg/s.
    >
    >Since the spacecraft will move rapidly, and may not be visible to the unaided 
    eye, observers need to quickly and
    >reliably move from one intercept point to the next, without relying on easy 
    visibility. If an automated pointing system
    >is used, its mechanism be sufficiently fast to move to the next intercept 
    point, to avoid missing the observation. If
    >manual star-hopping is to be used, then that also will take time, that must 
    be accounted for.
    >
    >The ephemeris is the most important tool for planning your strategy. 
    Yesterday, I posted an example, computed for Carlos
    >Bella, who is in a good location to observe part of burn #1:
    >
    >http://satobs.org/seesat_ref/phsrm/Phobos-Grunt_Ephemeris-v1_(sample).pdf
    >
    >I will be pleased to provide the MS-Excel spreadsheet used to generate the 
    ephemeris, on request. Not everyone uses
    >Excel, so I would be pleased to produce the ephemeris. I need only the 
    precise site coordinates, which should be
    >accurate to within 100 m.
    >
    >Time permitting, I am also willing to assist in planning an observer's 
    strategy. I will need information on the method
    >of observing, the observer's experience, physical obstructions that may block 
    the view of the track, etc.
    >
    >3. Near-Real-Time Data Requirement
    >
    >A significant challenge for observers is the requirement to report observed 
    data in near-real-time, which practically
    >means "as soon as possible".
    >
    >Prospective observers are requested to pre-register, and to report results 
    via this page:
    >
    >http://phobos.cosmos.ru/index.php?id=1686&L=2
    >
    >An example of the required format is shown at the bottom of that page. I have 
    reproduced it here, with my interpretation
    >of the key information:
    >          
    >             Date/time      R.A. and Dec (2000.0)   mag
    >         ---------------- ------------------------ ------
    >         yyyy mm dd.ddddd hh mm ss.sss+dd mm ss.ss  
    >Rosetta C2005 03 02.00860 11 05 08.545+02 24 23.95 16.1 V D0020557
    >
    >Elsewhere, the required format has been described as MPC 80-column. Since I 
    concentrate on artificial satellites, I
    >seldom encounter these formats, but my guess is that the above may be an 
    abbreviated version.
    >
    >Observers should be prepared to reduce their observations quickly and 
    reliably, to meet the near-time requirement.
    >
    >If there are observers who feel confident in their ability to obtain still or 
    video imagery, but need assistance with
    >data reduction, I am willing to assist, but please do not wait to the last 
    minute to make your request. I need to know
    >what form your data will take, so that I am prepared to handle it.
    >
    >4. Practice Makes Perfect
    >
    >If your astronomy specialty involves something other than observing 
    artificial satellites, then you should consider
    >practicing on a few satellites, to identify any problems in your proposed 
    methodology and gain some efficiency and
    >speed. The spacecraft will move rapidly, so planning and preparation are 
    essential to success.
    >
    >Happy hunting!
    >Ted Molczan
    >
    >
    >
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