Path: utzoo!attcan!uunet!lll-winken!ames!pasteur!ucbvax!LL-VLSI.ARPA!glenn
From: glenn@LL-VLSI.ARPA (Glenn Chapman)
Newsgroups: sci.space
Subject: Transmitter failure on Phobos II
Message-ID: <8901250634.AA26978@ll-vlsi.arpa>
Date: 25 Jan 89 06:34:13 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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     The USSR's Phobos II probe to Mars has suffered a "major hardware 
problem" with its communications, according to both Defense Daily and Soviet 
Areospace (Jan. 9th).  The main transmitter, a 50 Watt high data rate system, 
has failed almost completely, and there is little chance it can be recovered.  
This leaves only the 5 Watt low rate back up transmitter, obviously with 
little capacity for the imaging data of Mars/Phobos.  The high data rate 
system was to operate at 4000 bits per second, the same as the US Viking 
probes.  Roughly the new lower rate will be 1/10 of this (though some increase 
may be possible depending on the noise levels.  Note that the internal 
storage capacity on the Phobos probe is 30 Megbytes. 
     Russian researchers believe that they should still be able to get the 
data from the Phobos encounter on April 7.  The two Phobos surface probes, the 
base station and the hopper, have their own transmitters.  However, the initial 
Martian orbital data, slated to start on Jan 29th, will be drastically 
reduced.  The good news is that the three FREGAT television cameras and the 
connected spectrometer have been repaired after an earlier problem.  The 
computer has room for 1100 groups of pictures from the 4 instruments, hence 
the problem on the initial orbits.  Also one of 10 particle stream instruments 
has failed, but that is not considered critical (sorry I am not certain 
exactly which of the charged particle instrument they are referring to here).
All of this comes after the earlier total failure of Phobos I.
     According to earlier information the Russians should have started the 
final course corrections sometime between Jan. 14 to 22, but I have not heard 
of it.  Phobos will be heading towards Mars from the interplanetary orbit and 
reach about a minimum distance of 800 Km (500 miles) on the 29th.  At that 
point the retros will fire, to insert the craft into a highly elliptical orbit 
of 4200 Km (2610 mi) periares and 79,000 Km (49,100 mi.) apoares of 72 hours 
period (sorry - I am just guessing that they will combine the greek orbital 
prefixes with the greek name for Mars). It will maintain this orbit for 25 
days with the original plans calling for high resolution photos of Mars.  
    Note: for those trying to follow the Phobos missions the best source I 
have seen is the new book "Race to Mars" edited by Frank Miles and Nicholas 
Booth, Harper & Row pub. (1988) $19.95; Library of Congress call number 
TL799.M3R3.
    Sorry for the delay in this report (and my other Soviet program data) but 
I was off at a conference and have just gotten caught up from the January 
rush.  Also I must thank several people who sent kind notes with respect to my 
postings at the year's end - my net connections do not all me to reply to all 
of you but your interest is appreciated.

                                                  Glenn Chapman
                                                  MIT Lincoln Lab