1. Summary of GPR Systems for Mars Exploration
Alex Griffin

2. Why Ground Penetrating Radar(GPR) on Mars?
GPR used by Mars-orbiting satellites (SHARAD) in the past
Mars rovers examined stratigraphy using drilling and soil collection, which is very inefficient in terms of time compared to radar, so it can map geological properties over a much wider area.
Using GPR at the surface can be a way to quickly map a shallow stratigraphic column of an area with higher resolution at short depths than satellite-based GPR
Primary objective of upcoming rover missions is to discover signs of ancient life near the surface, and examine geological patterns.

3. Eurpean Space Agency(ESA) - WISDOM
Water Ice Subsurface Deposit Observation on Mars (WISDOM)
2020 Mission planned by the European Space Agency
Main objective of the mission is to search for evidence of ancient life
Plans to search icy subsurfaces
Searches a depth of 3m, has a 2m drill to take samples
Ultrahigh-frequency, stepped radar system

4. NASA - RIMFAX RIMFAX - Radar Imager for Mars’ Subsurface Experiment
2020 Scheduled Mars Rover Mission
Scientific objectives of mission include discovering signs of ancient life, analyzing geological records, characterizing the climate, and preparing for eventual human exploration. (
First Radar system to be sent to the surface of Mars by NASA

5. RIMFAX System Concepts to Know
Gated FMCW
Ultra-Wideband
Bow-tie slot Antenna

6. Gated FMCW FMCW is used to decrease necessary transmit power.
Gated FMCW - Use FMCW with one antenna by switching back and forth between receiving/transmitting.
Avoids use of a second antenna - saves weight, can use a larger antenna

7. Ultra-Wideband (UWB) Classified as very large bandwidth signals
Used because of low energy cost
Engineers don’t have to worry about frequency restriction laws like on Earth
Bow-Tie slot antenna(below) chosen for wideband operation, which is necessary for compatibility with UWB.

8. RIMFAX System Design Gated-FMCW Design
Space-Quality FPGA and DAC chips limits clock frequency
Sweep time of 1-20 ms depending on operation mode
Frequency sweep from MHz (exact sweep depends on operation mode)
Integration time for one radar sounding is 100 ms
Sampling distance between each sounding is 10 cm
10 sweeps per coherent integration
Minimum depth of about 10 m

9. RIMFAX System Operation
Shallow Mode - Use gating to observe surface reflectivity of the ground, use for future soundings
Reduced receiver gain or transmitting power when measuring the surface reflection, which limits the dynamic range
Second Mode - Modify gating to ignore

10. Matlab Analysis of RIMFAX Design for Reflection at 10 m
Parameters:
Frequency sweep: MHz
Sweep time: 1 ms
Target Depth: 1 m
Expected Beat Frequency: 7 kHz
Chosen Gating Frequency: 17 kHz (chosen above Nyquist Rate)

12. Gating acts as a Mixer

13. RIMFAX Field Test Field Test in Svalbard, Norway on Glacier
Mounted on snowmobile traveling at 20 km/hr

14. Questions?