NASA’s First Radio Telescope on the Moon: Radio wave Observations at the Lunar Surface of the photoElectron Sheath (ROLSES)

NASA’s Commercial Lunar Payload Services (CLPS) program allows rapid acquisition of lunar delivery services from commercial companies for payloads that advance capabilities for science, exploration, or commercial development of the Moon under the Artemis approach. It is a high-risk/high-reward initiative that could be a game-changer with regular delivery of science instruments to the lunar surface 2-3 times per year. One of the first science payloads scheduled to land on the Moon is the radio science experiment ROLSES. The NOVA-C lander built by Intuitive Machines is expected to descend to the lunar surface in mid-2023 in the south pole region near the Malapert A crater. ROLSES will deploy a set of four 2.5-meter radio antennas from the lander to then sense the radio and plasma wave environment between 2 kHz and 30 MHz. The ROLSES radio receiver is a software-defined radio spectrometer: the signals from each of the 4 antennas drive an isolating pre-amp and signal condition analog electronics. The broadband signals from each antenna are then digitized to 14 bits at 120M samples per second. The 4 digitized data streams are then digitally processed by a Field Programmable Gate Array (FPGA) that performs onboard spectral analysis via a Fast Fourier Transform (FFT). Time-averaged spectral values from the transforms are then stored and returned. The ROLSES science objectives include: (1) Measure the electron density in the local near-surface plasma via the local electron plasma frequency oscillation, (2) observe solar and planetary radio waves from a lunar surface observatory, especially now heading into the active solar maximum period, (3) detect terrestrial natural auroral and human-made radio emissions, to thus assess the Earth as a ‘noisy’ radio source, (4) sense interplanetary and ‘slow moving’ lunar dust via grain contacts with the antenna, (5) attempt to measure the Galactic background radiation below 30 MHz, and (6) assess the radio frequency interference (RFI) from the lunar lander, to thus determine the suitability of the lander as a radio observation platform.