Radar Imager for Mars' Subsurface Experiment

RIMFAX takes its name from Hrímfaxi, the horse in Norse mythology that "faithfully brings the night." The radar operates at radio frequencies of 150–1200 MHz and uses a Bow-Tie Slot antenna.

• Name — RIMFAX • Upright — 1.2 • Operator — NASA • Manufacturer — Norwegian Defence Research Establishment • Type — Ground-penetrating radar • Function — Study subsurface structure • Mass — 3 kg (6.6 lb) • Dimensions — 19.6 × 12.0 × 0.66 cm • Power Consumption — Max: 10 watts • Resolution — 15 cm to 30 cm (3" to 12") • Spacecraft — Perseverance • Sc Operator — NASA • Launch — 30 July 2020, 11:50:00 UTC • Rocket — Atlas V • Launch Site — Cape Canaveral, SLC-41 • Cospar — 2020-052A

RIMFAX is a ground-penetrating radar; its antenna is located on the lower rear of the Perseverance rover. It can image different ground densities, structural layers, buried rocks, meteorites, and detect underground water ice and salty brine at depth. Ground-penetrating radars (GPR) send radio frequency electromagnetic waves into the ground and then detect the reflected signals as a function of time to reveal subsurface structure as well as composition. RIMFAX is based on a number of GPR instruments developed at the Norwegian Defence Research Establishment (FFI). RIMFAX was selected by NASA to be one of the instruments on the Mars 2020 rover in July 2014. RIMFAX enables the science team to assess shallow layers and their stratigraphic relationships with nearby outcrops, thereby providing a window into the geological and associated environmental history. The RIMFAX instrument was developed and built by FFI and delivered to NASA's Jet Propulsion Laboratory for integration with the rover in December 2018. Due to Mars's 24.5-hour day, RIMFAX operations are shared between the University of California, Los Angeles (UCLA) and the University of Oslo (UiO), with the rotation every two weeks. The RIMFAX data is archived by NASA's Planetary Data System. The RIMFAX principal investigator is Svein-Erik Hamran of FFI, and his team includes scientists from Norway, Canada and the United States.

RIMFAX employs a gated Frequency Modulated Continuous Wave (FMCW) waveform to probe the subsurface. Gated FMCW uses a single antenna for both transmission and reception, quickly switching it between the transmitter and receiver modes. RIMFAX is commanded to acquire radar soundings every 10–20 cm along the rover's path to create two-dimensional GPR images of subsurface structure. • Illustration — RIMFAX – Bow-Tie Slot antenna • Specifications — Units/performance • Mass • Power — 5 to 10 watts • Dimensions — 19.6 × 12.0 × 0.66 cm (7.0" × 4.7" × 2.4") • Data return — 5 to 10 kbytes per sounding location • Frequency range — 150 to 1200 MHz • Vertical resolution — 15 cm to 30 cm (6" to 12") • Penetration depth — ≤ • Measurement interval — Every

An engineering model of RIMFAX was tested at several locations, primarily in Svalbard and the US Southwest. Modelling was carried out with gprMax, an open source electromagnetic simulation tool, to assess the imaging potential at the landing site. During development, a detection range of about 10 yards/meters was targeted, and tests on glaciers were successful.

Other Mars radar experiments include SHARAD, MARSIS, and WISDOM.