Wishes and Starshine update (long)

From: Daniel Deak (dan.deak@sympatico.ca)
Date: Mon Dec 31 2001 - 15:00:44 EST

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    Hi all,
    I'm back online after a week break. Having read a lot of mails about the
    Starshine satellites on different sat observers lists, I decided to call Gil
    Moore, Starshine project director, and discuss the visibility problems with him
    as well as solutions for future satellites.
    He is very grateful for all the observations reported on SeeSat and I join him
    in thanking everyone who tried successfully or not to see Starshine flashes. We
    still need a lot of observations, negative or not, of Starshine 3 in particular.
    Now, let's analyse what could be wrong with the Starshine satellites. First of
    all, here are the basic constraints for the design of these satellites. They
    must fit a 5 cu.ft. Hitchhiker canister to be installed in a Shuttle payload
    bay. With a 48 cm satellite diameter, there is a gap of about 3/4 inch all
    around between the sat and the canister wall. The maximum allowable weight is
    200 pounds (90 kg).
    One goal of the Starshine project is to have the maximum number of students
    involved in the manufacturing of satellite parts, maybe their once in a lifetime
    chance to touch something that will fly in space. That's why we have to fit the
    greatest number of mirrors on the relatively small surface of the sat. This
    will, in return, increase the chances of seeing a sunlight flash. For Starshine
    1 and 2, the number of allowable "slots" for mirrors or other hardware was 878
    because the hole pattern for the mirror stems had to be arranged in rows
    parallel to the sat equator due to the type of machine-tool and techniques used
    to drill the holes.
    The mirror diameter has been decided after studying what would be the minimum
    size along with the maximum spin rate that would permit a flash to be perceived
    by the eye's retina. Each mirror produces a sunlight reflection that measures a
    half-degree (sun's apparent dia. reflected on a flat surface). The desired spin
    rate has been established at 5 degrees per second (or one rev in 72 sec.) to
    have a flash duration of 1/10 second, just enough for the eye to make a good
    assessment of the relative brightness of the flash.
    The number of flashes seen on a single pass will depend on the actual spin rate
    of the sat, the orientation of the spin axis (flashes are in parallel rows) and,
    of course, the phase angle. If everything went according to plans, one observer
    should be able to see many flashes on a given pass unless he happens to be
    located between two rows of reflections on the Earth surface.
    Now, what happened with Starshine 1 and 2. Both sats are of similar design,
    number 2 having been built from spare parts from no. 1. Starshine 2 has 33 fewer
    mirrors because 31 laser retroreflectors and 2 miniature nozzles were installed.
    On both sats, the problem seems to be the lack of rotational motion. On the
    no.1, there was no mechanism to induce rotation. On no.2, there was one but it
    doesn't seem to have worked properly.
    It consisted of two small thrusters placed tangentially to the sat surface and
    in opposite directions. On ejection, a small rod protruding from under the sat
    activated a microswitch that sent an electrical signal to open a latch valve.
    This valve prevented nitrogen from escaping a small reservoir until needed.
    Because of NASA regulations, at no time was the pressure inside the reservoir
    allowed to exceed 100 psi. In addition, the valve was designed for much higher
    pressures and vibration testing showed some leakage, maybe because of that. So,
    due to the small volume of available nitrogen, the existing possibility of leaks
    and the temperature extremes of space, it is tought that there was not enough
    pressure remaining in the tank to make the satellite enter the proper tumbling
    Starshine 4 and 5 are now beeing designed. In the light of recent observation
    reports, a few changes are now discussed. We are looking at increasing the spin
    rate, adding more mirrors of different sizes (0.5, 0.75 and 1.0 in.) to better
    use the available space on the surface, changing the mirror pattern and mirror
    shape. The goal of all these measures is naturally to get more visible flashes.
    The mirror polishing campaign by students is getting under way right now with
    the first kits to be shipped on Jan. 17. A final decision should be made soon
    about which changes to implement.
    It has been discussed on this list (and I did the same with Mr. Moore last
    summer) that Starshine satellites do not make good targets for accurate visual
    positional measurements. Everyone agrees on that, given the way things turned
    out to be. If flashes were more frequent, then it would be possible for students
    to get the satellite position relative to the stars and use the data to make
    some works on orbital mechanics. The idea here is to get them involved in a
    space science project. The accurate enough data that is used to refine the
    models of the Earth's atmosphere is collected by radar, and also by laser for
    Starshine 2 and 3. To date, the data from Starshine 1 has been used by Dr.
    Judith Lean of the Naval Research Laboratory to measure the effects of solar
    extreme ultraviolet radiation on satellite orbital decay. She also plans to use
    all the rest of the satellites in the Starshine series to continue to improve
    their orbital decay prediction codes.
    Now, about Starshine 3. Since it was not contained in a canister, it could be
    manufactured a lot bigger. It's diameter was doubled. But due to the very short
    procurement time for the sat, we didn't have the time to manufacture and polish
    enough mirrors to make efficient use of the greater available space. With 1500
    mirrors, we should be able to get twice as many flashes as with Starshine 1 and
    2, as long as the spin rate is at the nominal 5 deg./sec.. The measured spin
    rate after deploy was one rev per 82 sec or 4.4 deg./sec.. This rate is
    calculated from the data received from the solar cell experiment mounted on the
    sat surface. We don't know how much this rate has been affected by the eddy
    current flowing through the structure because we lack recent telemetry reports
    from ham operators worldwide (I wont't discuss this matter further since it is
    off-topic). This is why we need as much visual sighting reports as possible to
    correlate the observations with the voltage fluctuations on the solar cells.
    I hope these details will help you better understand the purpose of the
    Starshine project and why the satellites are hard to spot these days. With this
    project, we also see here a good example of how the SeeSat list can be put to
    I will now wish everyone on this list a great year 2002, filled with a lot of
    clear night skies and exciting observations. Thanks to SeeSat, my three years as
    an amateur sat observer have been very exciting, I've come to know a lot of
    people virtually from all around the world and hope the list stays alive and
    well for many more years.
    Now, to conclude, here are the elsets I promised I would supply regularly to the
    list :
    1 26996U 01054B   01365.46065710  .00095646  00000-0  88452-3 0   212
    2 26996  51.6427 175.4880 0021479  59.9298 300.3861 15.66464235  2338
    1 26929U 01043A   01364.84427922  .00040424  00000-0  10638-2 0  1174
    2 26929  67.0501 199.8716 0004575 308.3150  51.7662 15.38341950 14068
    1 25544U 98067A   01365.52335958  .00067741  00000-0  77392-3 0  9069
    2 25544  51.6368 175.7007 0003034  78.4219  20.2844 15.61541982177871
    Best wishes,
    Daniel Deak
    representant, projet spatial Starshine
    L'Avenir, Quebec
    COSPAR site 1747 : 45.7275N, 72.3526W, 191 m., UTC-5:00
    Site en francais sur les satellites:
    French-language satellite web site : http://www.obsat.com
    Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org

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