TGO in orbit Options

[bobik]

A recent paper (full text available) on CaSSIS science planning contains some info about the rotation mechanism problems (#10) and especially about the consequences for science operations:

Another important event that triggered software changes at all levels were the motor issues CaSSIS experienced at the start of 2019. Although CaSSIS did recover part of the motor movement, at the time of writing the first 100 degrees of the full 360° rotation are not being used. Also the motor is being moved less frequently, with the end result that more images are acquired with a fixed motor position. In order to minimize the impact on the science, the tools were updated to take into account this fixed motor position. The CaSSIS team then identifies on a weekly basis a motor position that allows acquisition of many targets with a maximum of 20° misalignment with the spacecraft ground track. This provides almost full overlap of the colours in the CaSSIS focal plane so that colour imaging is efficient.

The tools were also updated to allow for stereo images and aligned single images that use the motor on an individual basis. As the CaSSIS teams has gained confidence the number of images allowed with these methods has been slowly increased to the point that is almost indistinguishable from the operations before the motor issues.

[volcanopele]

Yep, we are taking 5 stereo images per week to help reduce wear and tear on the motor mechanism. We are also taking up to 30 "aligned" images, where the motor is rotated to align with the image groundtrack. Otherwise a fixed motor position is used.