Sami Asmar, Supervisor, Radio Science and Systems Grou and Lead Radio Scientist in the DSN Science Office
Doug Johnston, Radio Science and Systems Group Member
This talk will describe the communications challenges encountered during the Cassini's Saturn Orbit Insertion and the preparation for and success in receiving useful information from Cassini.
The Cassini critical maneuver for Saturn Orbit Insertion was performed with the high gain antenna (HGA) pointed in the direction of travel through the ring plane during the engine firing. With the HGA pointed away from earth, a low gain antenna on the spacecraft's back side was utilized for monitoring the progress of the maneuver, it was not pointed optimally, resulting in very low signal levels received on the ground. The conditions of low signal levels and high frequency dynamics necessitated the use of the Deep Space Network's Radio Science Receivers to receive a carrier signal. A Doppler profile was constructed in real time to illustrate the progress of the maneuver and to indicate the performance of the spacecraft.
Sami Asmar is the supervisor of the Radio Science Systems Group and Task Lead Radio Scientist in the DSN Science Office. He has been leading a Cassini project task to develop the system and tools to acquire Radio Science data for the relativity experiments in cruise and planetary studies in the tour phase. He has also recently participated in the MER Entry, Descent and Landing communications task.
Doug Johnston is an analyst and software engineer in the Radio Science Systems Group. In addition to developing tools and analyzing data for the Cassini Radio Science experiments, he also supported the MER Entry, Descent and Landing task prior to developing a system to monitor the signal during the critical Cassini Saturn Orbit Insertion Maneuver.