17/11/2000 20:04:48
Subject:  - STRV 1c&d Progress


Dear All,


Both  spacecraft were successfully acquired yesterday and controlled from the
DERA  ground  station  at West Freugh and the DSN Madrid and Goldstone ground
stations.   Today  further contact has been made during the 4 hour visibility
from  West  Freugh  and  we  plan  another  link  session  tomorrow  morning.
Visibility  is  poor  on  Sunday but improves on Monday and we will therefore
take a 'rest day' before continuing to check out the spacecraft next week.

The  launch  sequence  appeared  to  be exactly to plan.  The Ariane-supplied
spin-up  of  both  spacecraft  has  been  confirmed at 1.7deg/minute. A solar
aspect  angle  of  approximately  95deg  for  1c  and  110deg for 1d has been
measured  using  the analogue sun sensors. These values are acceptable during
the LEOP. The residual nutation from the separation event of around ñ10deg on
1c  and  ñ20deg  on  1c  was  measured yesterday. Today, the SAA has remained
unchanged  and  the  nutation has halved on both vehicles under the action of
the  passive  nutation  damper.  This  trend is expected to continue over the
coming   days.   The  relatively  large  initial  nutation  on  1d  has  made
communications  slightly  more  difficult, but this is expected to improve as
the nutation declines.

All  onboard  temperatures  are  as  predicted,  all  payload experiments are
powered  off, and all subsystems are operating within normal parameters. Both
spacecraft  have  passed  through  their  two  eclipses  (each  of 20 minutes
duration)   without   event  and  with  temperatures  remaining  well  within
tolerance.    The  power  systems  are  operating  correctly  and  the  first
operational  spacecraft  Lithium  Ion  battery  in  space  has  now performed
faultlessly  since  launch.   The  gas  pressure on both spacecraft are fully
pressurised and STRV 1c has performed a spin-up test operation.  Satisfactory
digital  sun and Earth sensor readings have been taken, indicating that these
sensors are functioning correctly.

The  activities  over  the next several link sessions will be to increase the
spin  rate of both vehicles to 3 rpm and to perform a more detailed check out
of  the  onboard  systems.  Once  complete,  the  functional check out of the
experiments will commence.

The next update will be on Monday.

In the meantime, thank you very much for all the congratulations and good
wishes, which you have sent.  It means a lot to us.

best wishes

Richard