Timothy Bateman, UNSW Canberra Space; Ken Smart, CSIRO Space and Astronomy; Melrose Brown, UNSW Canberra Space
Keywords: Passive RF, SDA, Cislunar
Abstract:
There is a renewed focus on Space Missions to the Moon. The late 1950s and 1960s was the Golden Era of off planet space exploration, starting with artificial satellites and then increasingly focussed on the Moon, with the USA and the Soviet Union launching numerous missions. The triumph of the Space Race was the crewed Moon Landing by Apollo 11 in 1969. This was the 72nd mission to the Moon, and the last decade (2014-2024) has witnessed approximately 30 further Lunar missions. Now 10 countries of the Earth have reached the Lunar Surface, and the IM-1 mission in February 2024 has become the first private spacecraft to soft land on the Moon.
The United States has announced the Artemis program will return humans to the Moon this decade. A Lunar Gateway will be established in Lunar orbit adding to the 6 active lunar orbiters of July 2023. Enhanced capability in cislunar SDA (XDA) will be required as the Moon presents a challenging orbital environment with only a handful of stable orbits.
Observations of cislunar space present significant challenges due to the large distances involved and rapidly changing geometry. Trajectories in cislunar space are highly chaotic and maintaining custody can be very difficult. Sensor technologies can be broken into both active and passive methods in electro-optical and radio frequency systems. Active methods in electro-optical (laser ranging) and RF (radar) present a particular challenge due to the prohibitive power levels required. Passive electro-optical observations suffer from the issue that even though the object to be tracked is geometrically accessible, there may be poor illumination by the Sun. Additionally, the high albedo of the Moon presents dynamic range challenges for passive optical observations. Hence, passive RF methods can have significant benefit as the object itself is illuminating the sensor by transmitting RF signals, and only a receiver is required.
As new array radio telescopes are brought on-line, there is increasing scope to apply existing infrastructure to alternate uses, such as SDA.
In preparation for the return to the Moon, the NASA CAPSTONE mission serves as a pathfinder to study the orbit of the future Lunar Gateway. We evaluate the feasibility of using the CSIRO Mopra 22m Radio Telescope for the detection of RF emissions from Lunar orbiting spacecraft at X and S band. The results from an observational program are presented and demonstrate that RF emissions from CAPSTONE and other spacecraft are detected during periods of contact with the NASA DSN stations at Tidbinbilla, Australia and Goldstone, California. RF signal analysis detailing pattern of life is presented. Future work is detailed including Doppler processing and plans to perform Orbit Determination. Verification with actual position data from the mission is planned in addition to possible application of RF interferometry for precision location.
Date of Conference: September 17-20, 2024
Track: Cislunar SDA