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Spacecraft Status

H. Schweitzer and J.-P. Olive gave a report on the spacecraft status (see annex 4). The main conclusions are:

In order to simplify operations and reduce operations costs a proposal has been put forward by the FOT to reduce the number of roll steering law table updates. Presently, we have a table now with 400 entries, having 3 days worth of roll steering law data, covering 1 day plus 2 days autonomy for contingencies. With this resource, the spacecraft rolls every 11 minutes a max. (March and September) of approx. 3.5 arcsec (requirement on roll stability is 20 arcsec). It is proposed to increase the period to 22 min., making the table good for 4 days, but the roll steps are 7 arcsec in March/September, less in other months. FDF is presently checking, whether we can have guide stars for a four day time span. Question to the PIs was: can your observations tolerate a spacecraft roll of e.g. 7 arcsec every 22 min? Nobody present at the meeting anticipated a problem with that, but MDI would like to investigate it in more detail. There is an action on MDI to reply to the proposed roll steering law update scheme before end of October (Action 24-1).

Bernhard Fleck
Tue Jan 6 15:27:41 EST 1998