Chandrayaan-1 mission to the Moon

Goswami, J. N.; Annadurai, M.

doi:10.1016/j.actaastro.2008.05.013

Cited by 74 publications

(41 citation statements)

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“…Evidence by in-situ measurements from space craft including Lunar Prospector (1998-1999) [6], Kaguya (2007Kaguya ( -2009 [7], Chandrayaan-1 (2008-2009) [8] and Nozomi (1998) spacecraft [9], are consistent with the presence of collisionless shocks and the formation of minimagnetospheres. Because the observational data derives from a sequence of case studies from different missions [1,[10][11][12][13][14][15][16], it is to be expected that there is some variation in consistency.…”

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confidence: 77%

Minimagnetospheres above the Lunar Surface and the Formation of Lunar Swirls

et al. 2012

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In this paper we present in-situ satellite data, theory and laboratory validation that show how small scale collisionless shocks and mini-magnetospheres can form on the electron inertial scale length. The resulting retardation and deflection of the solar wind ions could be responsible for the unusual "lunar swirl" patterns seen on the surface of the Moon.Miniature magnetospheres have been found to exist above the lunar surface [1] and are closely related to features known as "lunar swirls" [2]. Mini-magnetospheres exhibit features that are characteristic of normal planetary magnetospheres namely a collisionless shock. Here we show that it is the electric field associated with the small scale collisionless shock that is responsible for deflecting the incoming solar wind around the minimagnetosphere. These ions impacting the lunar surface resulting in changes to the appearance of the albedo of the lunar "soil" [2]. The form of these swirl patterns therefore, must be dictated by the shapes of the collisionless shock.Collisionless shocks are a classic phenomena in plasma physics, ubiquitous in many space and astrophysical scenarios [3]. Well known examples of collisionless shocks exist in the heliosphere, where the shock is formed by the solar wind interacting with a magnetised planet. What is a surprise is the size of the mini-magnetospheres, of the order of several 100 km; orders of magnitude smaller than the planetary versions. Results from various lunar survey missions have built up a good picture of these collisionless shocks.These collisionless shocks have a characteristic structure in which the ions are reflected from a rather narrow layer, of the order of the electron skin depth c/ω pe (where c is the speed of light and ω pe is the electron plasma frequency), by an electrostatic field that is a consequence of the magnetised electrons and unmagnetised ions. The narrow discontinuity in the shock structure produces a specular reflected ion component with a velocity equal to or greater than the incoming solar wind velocity. The reflected ions from a counter-propagating component to the solar wind flow that form the magnetic foot region, which extends about an ion Larmor orbit upstream from the shock. This occurs when the Mach number (the ratio of flow velocity to Alfvén velocity) is of the order 3 or less.We have carried out laboratory experiments using a plasma wind tunnel, to investigate mini-magnetospheres

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confidence: 77%

Minimagnetospheres above the Lunar Surface and the Formation of Lunar Swirls

et al. 2012

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“…[3] As a follow-on to the Clementine and Earth based experiments, two orbital synthetic aperture radars (SARs) described by Spudis et al [2005Spudis et al [ , 2010, Goswami et al [2006], Raney [2006], Bussey et al [2007Bussey et al [ , 2008aBussey et al [ , 2008b, and Chin et al [2007] conducted imaging of the lunar surface, searching for the presence of ice deposits in the polar shadowed areas. These are the Chandrayaan-1 Mini-SAR operating at S band frequency (13 cm wavelength) and the Lunar Reconnaissance Orbiter (LRO) Mini-RF operating at S and X band frequencies (13 cm and 4.2 cm wavelengths), with the parameters shown in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Modeling radar scattering from icy lunar regoliths at 13 cm and 4 cm wavelengths

Thompson¹,

Ustinov²,

Heggy³

2011

J. Geophys. Res.

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[1] Two orbital synthetic aperture radars (SARs), the Chandrayaan-1 Mini-SAR (13 cm wavelength) and the Lunar Reconnaissance Orbiter (LRO) Mini-RF (13 and 4.2 cm wavelengths), have been imaging the lunar surface searching for ice deposits in the polar permanently shadowed areas. To understand the radar signatures of lunar polar ices, an empirical two-component model with parametric variations of the specular and diffuse components was developed and validated. This model estimates scattering differences associated with slopes, surface roughness, thin regolith over ice, and patches of ice. Lunar radar backscatter cross sections for the average surface for the Chandrayaan-1 and LRO instruments are estimated from the radar cross sections from the Moon at 3.8, 23, and 68 cm wavelengths measured in the 1960s at the Massachusetts Institute of Technology. This modeling predicts that enhanced diffuse scattering from near-surface ice can be separated from rocks if the scattering is characterized by both the high reflectivity and circular polarization ratios (CPRs) like those observed on Mercury, Mars, and the Galilean satellites. Scattering from near-surface ices covered by a thin regolith can be separated from rocks if the enhancement is twice the average or more. If, however, the lunar ice is dispersed throughout the regolith as ice-filling pores, then scattering differences might be too small to detect. Preliminary validation using LRO radar data for a few polar and midlatitude craters indicate that the observed CPRs are consistent with our models for different regolith ice and roughness conditions. Citation: Thompson, T. W., E. A. Ustinov, and E. Heggy (2011), Modeling radar scattering from icy lunar regoliths at 13 cm and 4 cm wavelengths,

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“…Examples include the American Lunar Reconnaissance Orbiter (Chin et al, 2006), the Chinese Chang'e mission (Sun and Dai, 2005), the Indian Chandrayaan mission (Goswami et al, 2006) and the Japanese SELENE mission (Sasaki et al, 1999). In order to make full use of the instruments on these missions, such as altimeters, the satellite orbit needs to be known with sufficient precision, preferably around the meter level.…”

Section: Introductionmentioning

confidence: 98%