A method to qualify the Rover Low Gain Antenna (RLGA) for use during the Mars Science Laboratory (MSL) mission has been devised. The RLGA antenna must survive all ground operations, plus the nominal 670 Martian sol mission that includes the summer and winter seasons of the Mars thermal environment. This qualification effort was performed to verify that the RLGA design, its bonding, and packaging processes are adequate.
The qualification test was designed to demonstrate a survival life of three times more than all expected ground testing, plus a nominal 670 Martian sol missions. Baseline RF tests and a visual inspection were performed on the RLGA hardware before the start of the qualification test. Functional intermittent RF tests were performed during thermal chamber breaks over the course of the complete qualification test. For the return loss measurements, the RLGA antenna was moved to a test area. A vector network analyzer was calibrated over the operational frequency range of the antenna. For the RLGA, a simple return loss measurement was performed.
A total of 2,010 (3×670 or 3 times mission thermal cycles) thermal cycles was performed. Visual inspection of the RLGA hardware did not show any anomalies due to the thermal cycling. The return loss measurement results of the RLGA antenna after the PQV (Package Qualification and Verification) test did not show any anomalies. The antenna pattern data taken before and after the PQV test at the uplink and downlink frequencies were unchanged. Therefore, the developed design of RLGA is qualified for a long-duration MSL mission.
This work was done by Rajeshuni Ramesham, Luis R. Amaro, Paula R. Brown, and Robert Usiskin of Caltech; and Jack L. Prater of Polytechnic High School for NASA’s Jet Propulsion Laboratory. NPO-48500
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Rover Low Gain Antenna Qualification for Deep Space Thermal Environments
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Overview
The document outlines the qualification efforts for the Rover Low Gain Antenna (RLGA), developed by NASA's Jet Propulsion Laboratory (JPL) for the Mars Science Laboratory (MSL) mission. The primary goal was to validate the RLGA's design and its ability to function effectively in the extreme thermal environments encountered on Mars, particularly during the planned operational lifetime of 670 Martian sols. To ensure reliability, the antenna was required to survive three times this duration, equating to 2010 sols without performance degradation.
The RLGA is a novel antenna designed for direct communication with Earth from the MSL rover deck. It features a choked waveguide horn with a parasitic dipole array, comprising key components such as the choked horn, polarizer, dipole cap, and a mounting bracket with a shorting plate. The qualification testing aimed to simulate the severe thermal cycles expected on Mars, which include significant temperature variations between summer and winter seasons.
The testing regimen involved subjecting the RLGA to 600 thermal cycles ranging from -130°C to +15°C to represent Martian winter conditions, and 1410 cycles from -105°C to +40°C for summer conditions. This comprehensive testing approach ensured that the total of 2010 thermal cycles met the design life margin requirement.
Prior to the qualification tests, baseline measurements were taken, including RF return loss and antenna radiation patterns, along with visual inspections. During the qualification process, functional intermittent RF tests were conducted at various intervals. The results indicated no anomalies in return loss measurements, and the antenna's radiation pattern remained unchanged before and after testing. Visual inspections also confirmed that there were no physical changes to the RLGA due to thermal cycling.
The successful qualification of the RLGA provides confidence in its performance for long-duration missions to Mars and sets a precedent for future NASA missions. The document emphasizes the importance of rigorous testing and validation in aerospace technology, ensuring that equipment can withstand the harsh conditions of space exploration. Overall, the RLGA's development and qualification represent a significant advancement in communication technology for deep space missions.
