Mini-RF S- and X-band Bistatic Observations of the

Lunar Exploration Analysis Group (LEAG)

October 10th, 2017

INTRODUCTION

Bistatic Campaigns • Mini-RF operated in concert with the Arecibo Observatory (AO) to collect S-band (λ = 12.6 cm) bistatic radar data of the lunar nearside from 2012 to 2015 (1st bistatic campaign).

• Mini-RF resumed operations in 2017 and is currently operating in concert with AO and GSSR DSS-13 to collect S- and X-band (λ = 4.2 cm) bistatic radar data of the lunar nearside (2nd bistatic campaign)

Nearside South Pole S-BAND OBSERVATIONS (1ST)

S-BAND OBSERVATIONS (1ST)

SUMMARY: 1ST CAMPAIGN

Patterson et al., 2017 SUMMARY: 1ST CAMPAIGN

Copernican crater ejecta • The responses observed for the continuous ejecta of the craters Byrgius A and Kepler indicate that rough surfaces observed at S-band (12.6 cm) radar wavelengths can produce an opposition effect.

- Clear differences in the character of the responses for the ejecta of the craters are present. • The response for the continuous ejecta of the crater Bouguer shows that not all rough surfaces observed at this wavelength produce an opposition effect.

- These characteristics suggest a relationship between the opposition response of crater ejecta and crater age. - Could be driven by progressive weathering of the ejecta shifting the block size-frequency distribution toward a range that an S-band radar is not sensitive to. - Suggests that Bouguer is older than Kepler. Patterson et al., 2017

SUMMARY: 1ST CAMPAIGN

Water ice at ? Cabeus 2013-127 • An apparent opposition response was observed within an a portion of Cabeus’s floor – indicative of a CBOE. • The response is not observed in association with permanently shadowed regions of Cabeus but it is in a region where water ice can be stable within the top meter of the surface [Paige et al., 2010]. • The character of the response is unique with Patterson et al., 2017 respect to all other lunar terrains observed during the Mini-RF bistatic campaign. SUMMARY: 1ST CAMPAIGN

Water ice at Cabeus? • The measured opposition response of the imaged portion of Cabeus’s floor is narrow and strong, indicative of a CBOE. • The response is not observed in association with permanently shadowed regions of Cabeus but it is in a region where water ice can be stable within the top meter of the surface [Paige et al., 2010]. • The character of the response is unique with respect to all other lunar terrains observed during the Mini-RF bistatic campaign. • However, the measured CPR of Cabeus floor materials for bistatic angles < 0.5° does not agree with our interpretation of water ice.

- These data were gathered by Mini-RF monostatic [Neish et al., 2011] and ground-based [e.g., et al., 2006] observations of the crater

- They are not consistent with CPR measurements at similar bistatic angles for other known icy materials [e.g,, Ostro et al., 1992; Harmon et al., 1994; Black et al., 2001]. OPERATIONS: 2ND CAMPAIGN

S-band operations – Arecibo Observatory • 4 targets acquired: Craters Schomberger A and Hercules and Mare Imbrium (2)

Schomberger A

Mare Imbrium OPERATIONS: 2ND CAMPAIGN

X-band operations – DSS-13 (DSN/GSSR) • 17 targets acquired: - Non-polar craters Anaxagoras (3), Kepler (1), Atlas (1) - Craters formed since 2009 (3) - Polar craters Cabeus (3) and Amundsen (1) - Mare Imbrium (1) - Nubium IMP (2) - Taurus Littrow pyroclastic deposit (2)

Floor of Casatus C SUMMARY: 2ND CAMPAIGN

Non-polar craters (Anaxagoras) SUMMARY: 2ND CAMPAIGN

Craters formed since 2009 (near B)

Mini-RF

LROC WAC SUMMARY: 2ND CAMPAIGN

Craters formed since 2009 (near Flamsteed B)

Mini-RF

LROC NAC SUMMARY: 2ND CAMPAIGN

Polar craters (Cabeus)

a b

a Floor of Casatus C Partially illuminated floor of Cabeus

a b SUMMARY: 2ND CAMPAIGN

Polar craters – the radar scattering properties of the upper 0.5 meter of lunar polar regolith • The floor of Cabeus crater differs from both polar highlands and other polar crater floors

Polar highlands

Amundsen floor Cabeus floor Cabeus floor Casatus floor SUMMARY: 2ND CAMPAIGN

Polar craters – an emerging picture? S-Band wavelengths (12.6 cm) • The scattering response for the floor of Cabeus crater is unique and suggests the presence of water ice - Necessitates deposits multiple wavelengths in thickness X-band wavelengths (4.2 cm)

• Initial results do not suggest a similar Polar highlands response for the floor of Cabeus crater Amundsen floor Cabeus floor

- Could indicate the approximate Cabeus floor Casatus floor depth to materials that do produce a CBOE (i.e., > 0.5 m) • The response of the Cabeus appears Cabeus floor (S-band) to differ from other crater floors and surrounding highland terrain