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Miniature Synthetic Aperture Radar (Mini-SAR)

NSSDCA ID: 2008-052A-10

Mission Name: Chandrayaan 1 Lunar Orbiter
Principal Investigator:Dr. Paul D. Spudis


The Miniature Synthetic Aperture Radar (Mini-SAR) is a small imaging radar designed primarily to map the scattering properties of the lunar poles in order to ascertain if water ice is present and if so, to determine its location and distribution. Concentrated ice exhibits an increase in radar reflectivity and enhancement of circular polarization ratio along the backscatter direction which can be measured by Mini-SAR, allowing construction of a map of the location of ice deposits. Mini-SAR will also be used to produce radar maps of the lunar surface near the poles.

The Mini-SAR transmits at a frequency of 2380 MHz (S-band, 12.6 cm wavelength) with a Left Circular Polarization (LCP) and receives both H and V linear polarization coherently. This permits full reconstruction of the Stokes parameter scattering matrix. From these parameters, circular polarization ratio (CPR, the ratio of same sense circular received power to opposite sense circular received power) is computed and rendered into image form. Mini-SAR can function as either a scatterometer or a synthetic aperture radar (ASAR) In scatterometer mode, Mini-SAR will point downwards (nadir-pointing) along the orbit ground track. The RCP and LCP returns will allow determination of the surface RF emissivity, near-normal incidence Fresnel reflectivity, meter-scale surface roughness, and circular polarization ratio. This information will give estimates of radar and physical surface parameters such as dielectric constant and porosity at a resolution of 1.2 km/pixel. In SAR mode the system is directed 45 degrees off-nadir, imaging a swath parallel to the orbital track by delay / Doppler methods. A complete mosaic in both RCP and LCP, with a resolution of 150 meters, is compiled in roughly two weeks with a SAR swath taken every third orbit. A single SAR path will last less than 10 minutes. The SAR mode is used sparingly because the high data rate precludes operation of the other instruments during SAR operation. The instrument minimum antenna gain is 24.97 dB and peek RF power is 20 W. A bistatic radar experiment was also planned in concert with the Lunar Reconnaissance Orbiter to allow imaging of the poles at a non-zero phase angle, which could provide definitive evidence of lunar water ice.

Alternate Names

  • Chandrayaan1/Mini-SAR
  • Mini-RF Forerunner
  • Mini-SAR
  • urn:nasa:pds:context:instrument:mrffr.ch1-orb

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Paul D. SpudisPrincipal InvestigatorApplied Physics

Selected References

  • Spudis, P., et al., Mini-SAR: An imaging radar experiment for the Chandrayaan-1 mission to the Moon, Curr. Sci., 96, No. 4, 533-539, Feb. 2009.
  • Spudis, P., et al., Mini-SAR: An imaging radar experiment for the Chandrayaan-1 mission to the Moon, Proc. of the 34th Lunar and Planetary Science Conf., No. 1153, Lunar and Planetary Institute, Houston, 2005.
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