Editing Phobos 1 (section)

==Mission profile==

The optical [[coronagraph]] that was part of the Terek experiment and  designed to observe the Sun was non-functional from launch.<ref name=Valníček />

=== Malfunction ===
On 2 September 1988, the expected transmission from ''Phobos 1'' was not received. This was traced to a faulty key-command that was sent on 28 August from ground control in [[Yevpatoria]]. Same as the case of [[Mariner 1]], a technician unintentionally left out a single hyphen in one of the keyed commands. All commands were supposed to be proofread by a computer before being transmitted, but the computer that checked code was malfunctioning. The technician violated procedure and transmitted the command before the computer could be fixed to proofread it.<ref>{{Cite journal|date=7 November 1988|title=Phobos-1 Revival Attempts Abandoned|journal=Aviation Week and Space Technology|publisher=Penton Media|volume=129|issue=19|id={{ProQuest|205980638}}}}{{Subscription required|via=[[ProQuest]]}}</ref> This minor alteration in code deactivated the [[Spacecraft attitude control|attitude thrusters]]. By losing its lock on the Sun, the spacecraft could no longer properly orient its solar arrays, thus depleting its batteries.<ref>{{Cite book|title=Soviet Robots in the Solar System |last1=Huntress|first1=Wesley|last2=Marov|first2=Mikhail|publisher=Praxis Publishing|year=2011|isbn=978-1-4419-7897-4|location=Chichester, UK|pages=380}}</ref><ref name=ScienceMag>{{cite journal |last1=WALDROP |first1=M. M. |title=Phobos at Mars: A Dramatic View—and Then Failure |journal=Science |date=8 September 1989 |volume=245 |issue=4922 |pages=1044–1045 |doi=10.1126/science.245.4922.1044 |pmid=17838799 |url=http://catless.ncl.ac.uk/Risks/9.24.html#subj3 |access-date=24 September 2018|url-access=subscription }}</ref>

Software instructions to turn off the probe's attitude control, normally a fatal operation, were part of a routine used when testing the spacecraft on the ground.  Normally this routine would be removed before launch.  However, the software was coded in [[Programmable read-only memory|PROM]]s, and so removing the test code would have required removing and replacing the entire computer.  Because of time pressure from the impending launch, engineers decided to leave the command sequence in, though it should never be used.  However, a single-character error in constructing an upload sequence resulted in the command executing, with subsequent loss of the spacecraft.{{r|ScienceMag}}

The error is also attributed to a political argument between Yevpatoria and Moscow over who should control the mission. Moscow won control responsibility, but Yevpatoria would be responsible for checking all transmitted commands. This further complicated the process of transmitting valid commands to the spacecraft.<ref>{{Cite book|title=Russian Planetary Exploration|last=Harvey|first=Brian|publisher=Praxis Publishing|year=2007|isbn=978-0-387-46343-8|location=Chichester, UK|pages=251}}</ref>