PFS issue on Venus Express, PFS scanner stuck in its closed position Options

[Rakhir]

Bad news for PFS. I hope they will be able to solve this issue.

The PFS scanner is stuck in its closed position.
Several attempts to move it were made at the time, but the instrument did not respond. Experts suspected a thermal problem by which low temperatures were blocking the rotation of the mechanism.
Another attempt to move the scanner was made on 16 March 2006, in warmer flight conditions. Unfortunately, the scanner remains stuck.

The next opportunity to perform another test on the spacecraft will be end of April, after the Venus Orbit Insertion.

From http://sci.esa.int/science-e/www/object/in...fobjectid=38964

[deglr6328]

I am only able to remember one instance where a stuck instrument cover was removed DURING the mission. The Viking Mars scoop cover that was shaken out over several days of back and forth motions of the motor controlling it. Are there more examples? All the others I can think of, Galileo HGA, Pioneer camera cover not popping off, Venera camera cover not popping off and some missions where solar panels fail to open, were never fixed....

[tty]

I am only able to remember one instance where a stuck instrument cover was removed DURING the mission. The Viking Mars scoop cover that was shaken out over several days of back and forth motions of the motor controlling it. Are there more examples? All the others I can think of, Galileo HGA, Pioneer camera cover not popping off, Venera camera cover not popping off and some missions where solar panels fail to open, were never fixed....

The original partial deployment of MARSIS was cured by heating the kinked boom on the "inside" of the kink.
However You are right that the prognosis is not god. I remember how they tried everything with the Galileo HGA, opening slowly, opening quickly, heating it, cooling it, repeated "slamming" with the deployment engine, no luck.

I add my personal rant. For simple one-time mission-critical deployment tasks pyro actuators are preferable. They are simple, cheap, very reliable, light and can be made redundant at a low cost/weight penalty (just add another charge with a separate firing circuit). Not that they would necessarily be usable in this particular case. Pyros are generally too violent for deploying delicate instrument, but when it comes to things like getting rid of covers and cutting cables they are the best.

tty