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Proposal Identification No.:

R2223

Date Received:

2006-Feb-28 16:12:13

Technical Page
Proposal Type: General Category: Observation Category: Total Time Requested: Prop osal Title: Urgent Planetary Radar Solar System 3 Hours

Bistatic Mars Express-Arecibo Radar Observations of the "Stealth" Region of

Mars
ABSTRACT:
The "Stealth" area was identified by Muhleman et al (SCIENCE, 253, 1508-1513, 1991) as being unique on Mars because it returns NO backscattered echo when illuminated by Earth-based radar. Surface models suggest that the material is very loosely compacted ash or other fine-grained volcanic debris. The loose compaction allows matching of centimeter-wavelength radar signals into the regolith where they are eventually absorbed. The fact that there is no echo at all requires that there be no embedded rocks or other discrete scatterers in the "dust" within one absorption length (perhaps meters); otherwise, there would be diffuse echoes at moderate to high incidence angles as is the case elsewhere on Mars. Starting in 2005, a series of bistatic radar experiments was begun using the Mars Express spacecraft. Radio signals at 3.6 and 13.1 cm wavelengths are beamed from the spacecraft toward the (moving) specular point on Mars' surface; echoes are captured with dual-polarization receivers at each wavelength at 70-m antennas of the NASA Deep Space Network. The forward specular scattering expected in these experiments complements the backscattering results from entirely Earth-based radar systems. Experiments have already been conducted over Mars' Residual South Polar Ice Cap (RSPIC), which appears usually BRIGHT to Earth-based radar. The MEX RSPIC results show a surface with "normal" scattering properties - except that the inferred dielectric constant is too high to be solid CO2, the main constituent assumed in LIMITED areas (perhaps smaller than the MEX footprint) from other data (Simpson et al., 2005 Fall AGU). The S-Band MEX bistatic radar experiment is 30 dB less sensitive than the companion X-Band experiment because of lower transmitter power and lower antenna gain on both ends. The addition of 10 dB in gain provided by Arecibo could be the difference between no detection and a usable signal in this area already expected to be a difficult target.

Name Richard Simpson

Institution Stanford University

E-mail rsimpson@magellan.stanford.edu

Phone 650-723-3525

Student no

Service Observing Request

Remot e Observing Request

X

None All of the observing run. Part of the observing run. Queue Observing

X

No Maybe Yes

1


Instrument Setup
S-band receiver Atmospheric Observation Instruments:

Sp ecial Equipment or setup:

none

RFI Considerations Frequency Ranges Planned
2280-2310

2