http://sdo.gsfc.nasa.gov/

The SDO Flight Dynamics Team is marching toward an uncertain launch date, but is working on many fronts to be launch ready nonetheless. The MOC Flight Dynamics System (FDS) software is in the midst of what could be its final “cleanup” release. However, the slipping launch date has deferred some Ground System Readiness Testing that is highly desirable to insure launch readiness. We continued to train and support internal and Project simulations to exercise team members, software and operational procedures. For the Launch and Early Orbit (L&EO) phase, the orbit circularization profile was updated each time a significant change in the input conditions was noted. The orbit circularization profile consists of 7 principal orbit raising maneuvers carried out over 19 days. This effort will place SDO in a +/- 0.5 degree longitude control box about a longitude of 102 degrees West. The NMBD has produced predictions on eclipses, nodal crossing times, longitude drift, and spacecraft TDRS and ground station coverage for both line of sight and the SDO omni antennas in an attitude dependent mode.

In 2008, the S-Band tracking service for the two newly constructed 18-meter SDO ground antennas at the White Sands Complex was certified by analysts in the GSFC Flight Dynamics Facility.

In the analysis area, inputs were updated to the link margin calculations for the ground antenna supporting SDO. Analysis by the SDO Attitude Control System team concluded that the gyros used to hold the spacecraft attitude during orbit raising maneuvers will be influenced by temperature. The MOC/FDS software will be modified to allow in-orbit calibration of the temperature dependence of these gyros. An attempt to gain insight into this issue during the recent SDO Thermal Vacuum testing proved inconclusive. In the orbit determination area, the use of Differenced One way Doppler data from two TDRSs in the initial orbit solution was studied showing promising results for this early but crucial computation.