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Critical Spacecraft-to-Earth Communications for Mars Exploration Rover (MER) entry, descent and landingFor planetary lander missions, the most challenging phase of the spacecraft to ground communications is during the entry, descent, and landing (EDL). As each 2003 Mars Exploration Rover (MER) enters the Martian atmosphere, it slows dramatically. The extreme acceleration and jerk cause extreme Doppler dynamics on the X-band signal received on Earth. When the vehicle slows sufficiently, the parachute is deployed, causing almost a step in deceleration. After parachute deployment, the lander is lowered beneath the parachute on a bridle. The swinging motion of the lander imparts high Doppler dynamics on the signal and causes the received signal strength to vary widely, due to changing antenna pointing angles. All this time, the vehicle transmits important health and status information that is especially critical if the landing is not successful. Even using the largest Deep Space Network antennas, the weak signal and high dynamics render it impossible to conduct reliable phase coherent communications. Therefore, a specialized form of frequency-shift-keying will be used. This paper describes the EDL scenario, the signal conditions, the methods used to detect and frequency-track the carrier and to detect the data modulation, and the resulting performance estimates.
Document ID
Document Type
Conference Paper
External Source(s)
Hurd, William J.
Estabrook, Polly
Racho, Caroline S.
Satorius, Edgar H.
Date Acquired
August 23, 2013
Publication Date
March 9, 2002
Subject Category
Lunar And Planetary Science And Exploration
Meeting Information
IEEE Aerospace Conference(Big Sky, MT)
Distribution Limits
entry, descent, and landing communications
high dynamics tracking
Mars Communications
Mars entry, descent, and landing (EDL)

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