Subject: Observations of STS 36 and its Payload
From:         Ted [email protected] (Ted Molczan)
Date:         1990/03/13




                    Observations of STS 36 and its Payload
                    --------------------------------------


                       (C) T.J. Molczan, Toronto, Canada


                                 March 13, 1990


In mid-February, I circulated a report called "STS 36 Observation Guide".
It was an invitation to observe the secret DoD mission.  It is doubtful that
many USENET subscribers had a good visibility window this time, so I was not
surprised at the small number of responses.  Fortunately, an observation
network was organized, and the following is a summary of its activities and
major findings.  I am providing it in an effort to build interest in
satellite observation.



1.0  Tracking and Observing the STS 36 Mission
     -----------------------------------------


1.1  The Observation Network
     -----------------------


A network of astronomers, mostly amateurs, observed the shuttle on each of
the five days that it was in orbit.  The network consisted of one very
experienced satellite observer in Scotland and a group of about two dozen
observers in five communities in Canada's North West Territories and Yukon,
and Alaska in the U.S.A.


I organized the North American group when it became clear that most of the
world's experienced satellite observers would not have the shuttle's orbit
in a visibility window during the mission.  None of the members of the group
were satellite observers, however many were fairly experienced amateur
astronomers. They were given instructions by phone and fax on how to make the required
observations.  Throughout the mission I supplied them with predictions for
the next day's passes, collected their observations, adjusted the orbital
elements when necessary and then distributed new predictions.


The network performed splendidly.  During the mission, the orbiter made
three manoeuvers, and the payload made one manoeuver, all of which were detected
through the network's observations.  Despite their inexperience, the North
American group produced very good observations.  I envied their being able
to observe the mission first hand, however I did not envy the -20 C to -30 C
temperature they had to endure!  The team in Yellowknife also assisted CBS
News in obtaining video tape of the orbiter's pass over the city on the
second day of the mission.  The video was taped and processed by local CBC
(Canadian Broadcasting Corporation) personnel for CBS.



1.2  Sequence of Events
     ------------------


The following table shows the major events of the mission, based on the
network's observations and de-classified shuttle orbital elements.  Note
that the REV column is the revolution number.  NASA's rev numbering method
was used.  NASA calls the portion from liftoff to the first ascending node
(north bound equator crossing) rev 1.  Rev 2 starts at the first ascending
node.  The rev numbers below are the position within the current rev, not
the elapsed number of revs.  To obtain the latter, subtract 1.



   DATE     UTC   dd hh mm   REV    Alt  km              Event
---------  -----  --------   ----   -------   ----------------------------
28 Feb 90  07:50  00 00 00    1     zero      Lift-off


           08:50  00 01 00    1     204x216   From NORAD elset.


           10:45  00 02 55    3.0   207x216   From NORAD elset.


           12:32  00 04 42    4.2   250x261   OBS at Yellowknife, NWT.
                                              Obs indicated that orbit had
                                              been raised after rev 3.


           14:00  00 06 10    5.2   250x261   OBS at Whitehorse, Yukon.
                                              OBS at Yellowknife, NWT, 2 min
                                              later.


           15:10  00 07 20    6.0   250x261   From NORAD elset.


           15:31  00 07 41    6.2   250x261   OBS at Fairbanks, Alaska.


01 Mar 90  10:41  01 02 51   19.1   248x260   From NORAD elset.


           12:23  01 04 33   20.2   248x260   OBS at Yellowknife, NWT.
                                              Only orbiter seen.


           13:54  01 06 04   21.2   248x260   OBS at Yellowknife, NWT.
                                              Only orbiter seen.


           15:23  01 07 33   22.2   248x260   OBS at Whitehorse, Yukon.
                                              Only orbiter seen.


           18:01  01 10 11   24.0   248x260   From NORAD elset.


           19:10  01 11 20   24.8   245x249   From NORAD elset. Note result
                                              of burn to separate from
                                              payload.


02 Mar 90  06:18  01 22 28   32.3   245x249   OBS in Scotland. Payload
                                              seen, still in 248x260 km
                                              orbit, 57 seconds in time
                                              behind orbiter.


           10:25  02 02 35   35.0   245x248   From NORAD elset.


           12:13  02 04 23   36.2   245x248   OBS at Yellowknife, NWT.
                                              Payload observed, still in
                                              248x260 km orbit.


           13:44  02 05 54   37.2   245x248   OBS at Yellowknife, NWT.
                                              Payload in 248x260 km orbit,
                                              75 seconds in time behind
                                              orbiter.


           15:50  02 08 00   38.6   245x248   From NORAD elset.


           20:48  02 12 58   42.0   245x248   From NORAD elset.


03 Mar 90  01:45  02 17 55   45.3   245x248   Approximate time that payload
                                              manoeuvered to 271 km mean
                                              altitude. Determined from obs
                                              at 12:32, Mar 3rd; 05:52 and
                                              12:18, Mar 4th. See below.


           11:41  03 03 51   52.0   244x247   From NORAD elset.


           12:00  03 04 10   52.2   223x247   From NORAD elset.
                                              Result of rev 52 manoeuver.


           12:32  03 04 42   52.6   223x247   OBS at Yellowknife, NWT. Saw
                                              orbiter, followed 6m 20s later
                                              by payload. Payload was 2.65 min
                                              late re its deployment orbit,
                                              indicating it had raised its
                                              orbit.


04 Mar 90  05:52  03 22 02   64.3   223x245   OBS in Scotland. Saw orbiter,
                                              followed 13.1 m later by
                                              payload, which was 6.275 min
                                              late re its deployment orbit.


           11:41  04 03 51   68.2   223x245   NORAD elset.


           12:18  04 04 28   68.6   223x245   OBS at Yellowknife. Saw orbiter,
                                              followed 16.0 min later by
                                              payload. Payload was 7.983 min
                                              late re its deployment orbit.


           18:10  04 10 20   72.6   zero      Landed at Edward's AFB.



1.3  Findings
     --------


1.3.1  Payload is Very Large
       ---------------------


The major finding was that the payload is visually a very bright object, and
therefore probably very large.  On near overhead, well illuminated passes,
it had a visual magnitude between 0 and -1.5.  Even on a 15 deg elevation pass,
with only fair illumination it was between magnitude 1.2 and 1.6.  The
average standard magnitude (at range of 1000 km, and 50% illuminated) was about 1.6,
however more observations are required to obtain a high confidence value.
In any case, it is clear that this should be a relatively easy object to track.


The payload's brightness is in the same class as the KH-9 and KH-11
photorecon satellites.  Perhaps this is the long awaited KH-12.  According to a
pre-launch article in Aviation Week magazine, the payload is called AFP-731,
has a mass of 16.9 tonnes, and is designed for digital imaging
reconnaissance and signal intelligence.



1.3.2  A New Shuttle Payload
       ---------------------


Pre-flight, a couple of reporters had been told by sources that this payload
was the same as one flown on a past, high inclination DoD shuttle mission.
That would have made it a Lacrosse (STS 27) or a "Flasher" (STS 28).  In
fact, the STS 36 payload does not resemble either one of those.  It was brighter
than Lacrosse, and lacked its characteristic red colour (caused by lots of
gold kapton thermal blanketting no doubt).  It was much brighter than
"Flasher" and it did not flash.



1.3.3  Deployment Appeared to be Late
       ------------------------------


The payload had been expected to be deployed at 27 hours into the mission.
Observations on three passes between 28.5 and 31.5 hours into the mission,
revealed only the orbiter.  Observations on day 3 (later confirmed by NORAD
elsets) revealed that the orbiter moved to a slightly lower orbit sometime
between 34.2 h and 35.3 h, which was its manoeuver to separate from the
payload.  Therefore deployment probably occured between 31.5 h and 35.3 h.
It is possible that it occured earlier, and that the spacecraft were too
close together to separate with binoculars.



2.0  Future Activities
     -----------------


Now that the mission is over, experienced satellite observers will continue
to track the payload.  For the moment, we do not know the exact location of the
object.  The main reason is that it is not currently in a visibility window
for most observers.  In any case it is reasonable to expect it to move to a
higher orbit, which will necessitate a search.  Lacrosse and "Flasher"
manoeuvered to higher orbits about one week post deployment. If it is a
member of the KH series, then the STS 36 payload may move to a 300 km x 1000 km
orbit, like the three KH-11's currently in orbit.  We should know within the
next few weeks, as the orbit begins to move into visibility at the more
populated latitudes, where most of the observers are located.


Experienced satellite observers are welcome to get involved in the search.
I have prepared a report on search techniques, visibility windows and the
required observations.  Only those who contribute to the effort will share
in the details of what is learned, such as orbital elements.  Let me know of
your interest.
--
Ted [email protected]