Download Evolution of Planetary Science Activities in SPL

Evolution of Planetary Sciences in SPL
Anil Bhardwaj
Head, Planetary Science Branch
The research in the area of Planetary Sciences started about two decades back. Initially, the
research was largely aimed at developing theoretical models for explaining new
observations made either by planetary spacecraft-based instruments or by space-based or
ground-based telescopes. The studies include aurora and airglow emissions in the
atmospheres of the outer planets and ultraviolet emissions of comets. In the latter half of
1990s the study on Io – the innermost Galilean satellite – started with development of a
model to understand the degradation of electrons in SO2, since Io is the most volcanically
active planetary body in the solar system. Theoretical models using Monte Carlo techniques
were built that incorporated Galileo spacecraft measured information in the model and
explained the HST-observed emission on Io.
In the beginning of new millennium, the scope of planetary research expanded to making
use of space-based telescope. It started with the observation of X-ray emissions from Jupiter
system using NASA’s Chandra X-ray Observatory. This led to the discovery of “pulsating Xray hot-spot” in the Jupiter’s aurora, and X-rays from Io, Europa and Io Plasma Torus. The xray observations were extended to Saturnian system and strengthened with the use of
XMM-Newton X-ray Observatory. X-rays from the rings of Saturn were discovered. Further,
a direct correlation of x-rays from the disk of Jupiter and Saturn with those from the Sun
was established for the first time: suggesting that the x-rays from these giant planets can be
used to study the flares on Sun’s hemisphere which is not visible from the Earth. Many of
these “discovery-class” findings made the Press Releases by NASA and ESA (European Space
Agency). The work of studying X-ray emissions from planets was further enlarged to include
Mars, Venus, and Earth. The first unambiguous detection of X-rays from Mars exosphere as
well as the first soft (<2 keV) x-rays from Earth’s aurora were made during observations
made in 2003-2004 period.
Around this time a new dimension was added: the use of Giant Metrewave Radio Telescope
(GMRT) to study radio emissions from Jupiter. The first observation of Jupiter’s Synchrotron
Radio (JSR) emissions using GMRT was carried out in February-March 2003. This was
followed with GMRT observations of Jupiter in 2007 and 2008 to understand the short-term
variability in JSR emission. In 2011 the GMRT-radio observations of Jupiter were made in
concurrence with infrared observations using NASA’s Infrared Telescope Facility (IRTF) in
Hawaii. Recently, these radio and IR observations are clubbed with simultaneous ultraviolet
observations using HST and just launched Japanese SPRINT-A space-based UV-telescope.
The radio observations using GMRT are now being further grown with the application to
study surface and sub-surface thermal properties of Venus and Moon.
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The start of new millennium also brought the era of planetary exploration in India with the
Prime Minster announcing the first Indian Lunar Mission Chandrayaan-1 on 15 August 2003.
SPL responded to the call for proposals for experiment on the Chandrayaan-1 mission with
the SARA (Sub-keV Atom Reflecting Analyzer) instrument, which was a joint Indo-Swedish
collaboration with contributions from Japan and Switzerland. The experiment SARA was first
of its kind to study Moon by employing the Energetic Neutral Atom (ENA) imaging
technique. When the responsibility to develop Moon Impact Probe (MIP) was given to VSSC,
SPL came up with innovative experiment ChACE (Chandra’s Altitudinal Composition
Explorer) aboard MIP. Both SARA and ChACE gave SPL the required impetus to work on the
development of space-worthy payloads and related activities. The SARA and ChACE have
contributed immensely to lunar science – on the topic of the solar wind interaction with
Moon and the tenuous lunar exosphere. SARA discovered “Mini-magnetosphere” on Moon:
the smallest know magnetosphere in the solar system, and found that one in five of the
solar wind particles impacting the lunar surface are reflected back to space. On the other
hand, ChACE discovered the presence of neutral H2O and CO2 in the rarefied medium
around Moon.
Soon after the Chandrayaan-1 launch, the plans for the Chandrayaan-2 mission and a
mission to Mars were initiated, and SPL’s involvement started right from the study phase for
these missions. On the Mars Orbiter Mission (MOM) SPL’s payload MENCA (Mars Exospheric
Neutral Composition Analyser) will study the composition and distribution of Martian
exosphere, which will eventfully led to better understanding of the escape of Mars
atmosphere. MENCA was developed, tested, and qualified in a short time of about 18
months. On 13 November 2013, eight days after the MOM launch on 5 November, the
MENCA instrument has been successfully commissioned in orbit by operating for one hour
and its health was found to be normal.
The CHACE-2 experiment selected to be flown on the Chandrayaan-2 Orbiter will be a
sequel of the ChACE aboard MIP/Chandrayaan-1. With CHACE-2 we hope to learn the
diurnal variation in the composition and distribution of lunar exosphere and its variability
with lunation and solar flux.
With India taking up the indigenous development of Lander for the Chandrayaan-2 mission,
SPL proposed for exploring the ionosphere of Moon by a suit of experiments on the Lander
called RAMBHA (Radio Anatomy of Moon Bound Hypersensitive Ionosphere and
Atmosphere). RAMBHA consist of three instruments – Radio Sounder, Langmuir Probe, and
Dual-frequency Radio Communication system– each of them will provide unique and
distinct information about the lunar ionosphere.
With the availability of Chandrayaan-2’s Lander platform, SPL has embarked in the area of
exploring in-situ the thermal properties of the surface and sub-surface of Moon. The
proposed experiment ChaSTE (Chandra’s Surface Thermophysical Experiment) will measure
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temperatures near polar region in the first few centimetres of the regolith, where drastic
vertical temperature gradients are expected.
Close on the heels of the launch of Chandrayaan-1 mission, SPL initiated activities to
develop low-energy plasma analyser. Extensive ion-optics simulation carried out using
SIMION resulted in design of a novel but simple plasma analyser PLEX (Plasma Energy
Explorer) and an advanced version named LEIMA (Low Energy Ion Mass Analyser). A
modified and extended version of PLEX named PAPA (Plasma Analyser Package for Aditya)
has been recently selected for the Aditya-L1 mission which is meant for studying the solar
wind. PAPA is a combination of electron and ion energy analyser along with a TOF (Time-ofFlight) capability to analyse the mass of ions. PAPA would study the energy distribution and
its characteristics of solar wind from the L1 point, since L1 provides a vantage location to
look continuously at processes happening on the Sun.
In is important to mention here that the space-borne payload development activities in SPL
are ably supported by various Entities of VSSC.
Though during the last one decade or so SPL ventured into new realms of the planetary
observation using ground- and space-based telescopes and the development of payload for
missions, the study of processes in the solar system bodies using theoretical calculations
continue to grow. New models were developed to explain the dayglow emissions on Mars
that are recently observed by Mars Express mission – starting with a Monte Carlo model for
degradation of electrons in CO2 gas: the dominant constituent in the atmospheres of Mars
and Venus. Predictions made for the dayglow intensities of CO Cameroon band and CO2+ UV
doublet band emissions on Venus are found to be in accord with the first detection of these
emissions made by the SPICAV experiment aboard Venus Express mission. The calculations
are extended to Titan, the largest satellite of Saturn, where N2 Vegard-Kaplan band
emissions recently observed by Casssini UVIS were explained. Moreover, new models are
developed for visible emissions on comets. The photochemistry of red and green lines of
atomic oxygen, which are used as a proxy for estimating the water production rates in
comets, have been studied in detail at different heliocentric distances. Recent calculations
of emission intensity of CO Cameron band and atomic oxygen visible emission lines in
comets have considerably changed the existing concepts and the way species
concentrations were inferred from the observed emission intensities.
With SPL taking the development of space-borne instruments in a big way, a state-of-art
High Vacuum Space Simulation Facility (HVSSF) has been set up at SPL. The HVSSF is a 1metre class chamber providing vacuum of the order of 10-7 Torr in just few hour using dual
chain pumping system. It has ten 160 CF ports, ten 35 CF ports, and two 200 CF ports with
monolithic fused Quartz for Infrared and optical viewing. Full operation of the HVSSF is
controlled by a PC based-SCADA (Supervisor controller and data acquisition system). The
HVSSF is equipped with ion and electron sources for characterization of detectors, and
testing and calibration of plasma analyzers and neutral mass spectrometers.
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The contributions of SPL scientists in the area Planetary Sciences has been acknowledged
nationally as well as internationally – with election to the President-ship of PS Section of
Asia Oceania Geosciences Society, Vice-Chair of COSPAR Commission B, election to
Fellowship of National Academies, nomination to INSA-International Council of Scientific
Union committee, Editorship of international journals in planetary sciences, etc, and most
importantly bagging the Shanti Swarup Bhatanagar Prize for work in planetary sciences in
year 2007.
SPL has also made a strong contribution to the planning and commencement of the PLANEX
program of ISRO. The 3rd PLANEX workshop was held in SPL during February 2003.
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Discovery of X-rays from the rings of Saturn made using NASA’ Chandra X-ray Observatory.
The diffused blue-coloured areas superimposed on the optical image of Saturn and its rings
are the X-ray emissions.
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Flight models of CENA, SWIM and DPU of the SARA experiment flown on the first Indian
lunar mission Chandrayaan-1.
Schematics showing the accommodation of CENA, SWIM, and DPU of SARA experiment and
of CHACE/MIP on board Chandrayaan-1 spacecraft.
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The “Mini-magnetosphere on the Moon” discovered by the SARA experiment aboard
Chandrayaan-1 made the Cover page of 16 March 2010 issue of American journal
‘Geophysical Research Letters’.
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Left: GMRT image of Jupiter at 610 MHz obtained on 26 Feb. 2003 at 1848 UT. This is the first use of
GMRT to study the synchrotron radio emissions of Jupiter.
Right: A view of a few of the 30 numbers of 45 metre dish-antennas of GMRT. The GMRT
dishes are arranged in a Y-shape configuration, with longest base line of 25 km.
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The Flight model of the MENCA instrument aboard the Mars Orbiter Mission 2013.
Director VSSC Shri S. Ramkrishnan flagging off MENCA payload at SPL on 10 July 2013.
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High Vacuum Space Simulation Facility (HVSSF) of SPL, which is used for development,
testing, and calibration of space-borne payloads.
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Group Photo of attendees of the 3rd PLANEX Workshop on "Planetary Atmospheres,
Ionospheres, and Magnetospheres", held at SPL, VSSC during 17-22 February 2003.
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