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

[Guest_BruceMoomaw_*]

It might be possible to add such a spectrometer to (say) Bruce Campbell's "VISTA" Venus radar orbiter -- but the trouble is that the proposals for the next Discovery mission are, I believe, already past due. Certainly we have here further proof that the enduring bane of spacecraft is moving parts, and that more attention should be paid to this problem.

[gpurcell]

It might be possible to add such a spectrometer to (say) Bruce Campbell's "VISTA" Venus radar orbiter -- but the trouble is that the proposals for the next Discovery mission are, I believe, already past due. Certainly we have here further proof that the enduring bane of spacecraft is moving parts, and that more attention should be paid to this problem.

Bruce, would the procurement rules for Discovery allow a PI to add capacity to a mission if it is selected as a candidate for further study?

[JRehling]

Messenger has two spectrometers and is making a flyby of Venus. Atmospheres are better mixed than surfaces: one great flyby might do a lot of the good as far as composition goes.

Solomon et al [2006] says of the flyby: <<MDIS will image the nightside in near-infrared bands, and color and higher-resolution monochrome mosaics will be made of both the approaching and departing hemispheres. The UVVS will make profiles ofatmospheric species on the dayside and nightside as well as observations of the exospheric tail on departure. The VIRS will observe the planet near closest approach to sense cloud chemical proper-ties and near-infrared returns from the surface.>>

VEx can perhaps image the same areas at or (with not total loss of purpose -- the cloud formations don't utterly remake themselves in hours) a day or so before or after the Messenger observations.

Messenger's VIRS covers from 300nm to 1.45 microns (through the entire visible range) and will have resolution as good as 100 m at Mercury. I think along with the other instruments on VEx, the loss of science regarding atmospheric composition will be seriously blunted.

What's really lost with PFS is an ongoing record of temperature scans to correlate with vis/UV images of the clouds. Adding such an instrument to a radar orbiter would not mean as much without having vis/UV imaging to go along with it, and adding two major instruments to a planned craft is a heck of a redesign.

Remember, Japan is still planning to launch a Venus orbiter that *would* have pretty much these capabilities and arrive in 2010. This could be a big moment for Japan if they can get the data on the circulation.