glenn@LL-VLSI.ARPA (Glenn Chapman) (04/01/89)
On Mar. 29th the Soviet Union's Phobos II probe suffered a fatal
failure. On Mar. 21st it had undergone the final maneuver, placing it in
synchronous orbit with the Martian moon. On Mar. 26th pictures of Phobos
had been taken from about 150 Km (94 mi) from away. On the 27/28th a second
close up set was being taken. This was to generate the final orbital
measurements to insure the close approach could be done about 1 week later.
On the Phobos probes the antenna system is not mounted on its own transport
platform (as is done on most US probes). Instead the vehicle was commanded
to turn away, take the pictures, then return contact to Earth control.
However, in this case the probe rotated away, but never came back.
Compounding the problem of regaining command was the fact that it had
previously lost its main transponder, a 50 Watt system, and was now
operating on this 5 Watt backup. Thus there are two main probable failure
points, the first being that the control system broke down thus leaving the
probe unable to get back to Earth alignment. The other possibility is that
the transmitter died, and there was no backup left. Electronic equipment
often fails just when it is turned on again, as would be the case with this
observation method (the 30 Megabit memory could hold 1100 picture sets so
there was no need to transmit these in real time). It is not obvious which
problem occurred here though some reports say that faint signals were
received from Phobos II after this failure. The NY Times quotes Nikotal
Simyonov as saying "it would be very difficult at this point to get a
response form the spacecraft". The more time the craft is without earth
command the more likely it will loss the sun alignment for its solar cells,
thus suffering a power deficit also.
Note that the mission was not a complete failure. Even with the data
obtained at this point the probe has produced the "the highest quality
images of yet obtained of Phobos". In addition at Mars itself the infrared
spectra give much compositionial information about the planet's surface and
atmosphere, while the planetary magnetic field has been measured. Never
the less there is bitter loss at missing the Phobos landing by only a few
days. (Boston Globe and New York Times, Mar. 30)
One comment here, the researchers at the Soviet IKI institute, which
were in charge of the probe, have been pushing the line that unmanned
systems are cheaper and more reliable than manned ones. They have been
strongly suggesting that robots would be better to explore Mars rather than
a manned mission. After this high profile mission failure they could find
their case substantially harder to present in the USSR.
[Personal note - why is it that things only go really wrong with the
Russian program when I am off on a trip, and hence without my shortwave.
At one earlier conference the Soyuz TM-6 re-entry problem occurred. Sorry
for the delay in posting this but I just got back.]
So the Russians failed in this attempt on Mars. It was a loss to us
all (no US probe for Phobos is scheduled yet, and probably would not occur
before 2000 AD). It will be interesting to see if they launch a second try
in the 1990 or 1992 windows, if they can analyze the failure cause.
Glenn Chapman
MIT Lincoln Labstolfi@jumbo.dec.com (Jorge Stolfi) (04/02/89)
First of all, I wish to thank Glenn Chapman for his *very* valuable postings. They alone are reason enough to subscribe to this newsgroup. Still, I can't resist replying to his editorial: > > One comment here, the researchers at the Soviet IKI institute, > which were in charge of the probe, have been pushing the line > that unmanned systems are cheaper and more reliable than manned > ones. They have been strongly suggesting that robots would be > better to explore Mars rather than a manned mission. > After this high profile mission failure they could find their > case substantially harder to present in the USSR. Well, it is certainly true that all manned Mars missions to date were 100% successful and cost practically nothing. I am even willing to believe that this will remain true for many, many years to come. Unfortunately, those missions haven't return much useful data, have they... ;-) Jorge Stolfi --------------------------------------------------------------------------- ``I mean it is not enough to launch a projectile and give it no further thought. We must follow it throughout its course, until the moment it hits the target.'' ``Well!'' exclamed the general and the major, a bit taken aback by the idea. ``Absolutely,'' Barbicane spoke with self-assurance. ``Absolutely. Otherwise the experiment would be pointless.'' --Verne, _From the Earth to the Moon_ (1865) --------------------------------------------------------------------------- DISCLAIMER: The above opinions are just opinions.
jmckerna@polyslo.CalPoly.EDU (John McKernan) (04/02/89)
Friday's LA Times had some interesting speculation as to the underlying causes of the problems with the Phobos probes. They said the probes were the first of a new type manufactured by a government contractor independent of the scientists at the "Soviet Space Research Institute". The Times said that these basic probes (to which the various experiments and other unique hardware are added) have poor communication and computer facilities, and little redundancy, and that they are the cause of the phobos problems. Appearantly the USA is not the only country which has problems with lowest bid hardware from independent government contractors. John L. McKernan. Student, Computer Science, Cal Poly S.L.O. -------------------------------------------------------------------------------