CHANDRAYAAN - 2 EXPLAINED
Introduction
The Chandrayaan-2 is an ISRO mission that aims to place an orbiter around the moon and send a lander with a rover to its surface in 2015.
The mission is being undertaken in collaboration with Roskosmos of Russia.
Under an agreement signed on November 12, 2007 between the space agencies of India and Russia, ISRO and Roskosmos, each agency was to contribute Rs 425 crore towards the cost of the mission.
The spacecraft was to be launched in 2014, with an orbiter made by ISRO and a lander made by Russian Space Agency Roscosmos. The lander was to carry a small Indian built rover to collect and examine lunar soil samples, Russians refer to the project as Luna-Resource.
Roskosmos Dropout?
On January 21, 2013, Dr. S.V.S. Murty of the Planetary Exploration Group of the Physical Research Laboratory (PRL), an institution in Ahmedabad under ISRO, announced that India would undertake the Chandrayaan mission all by itself, dropping earlier plans of collaborating with Russia. [via The Hindu]
Dr. Murty was speaking on India’s lunar and Mars missions at a workshop on exoplanets at the laboratory.
ISRO took the decision to go it alone after Russia's Roskosmos expressed its inability to provide the lander for the mission, following the failure of the Russian Phobos-Grunt mission to Mars in November 2011.
ISRO will now make the orbiter, lander and rover all in-house.
SAC has completed the design of the indigenous lander and preliminary configuration study, according to Murty. The mission profile has undergone minor alterations.
The Chandrayaan-2 will be launched using a GSLV powered by an indigenous cryogenic engine in 2015.
The Orbiter will have five primary payloads, two of which will be improvements on instruments that were onboard Chandrayaan-1.
The rover too will carry two additional instruments.
According to PRL director Jitendra Goswami, despite the Russian pull out from the Chandrayaan project, Indo-Russian collaboration in planetary exploration will continue.
Chandrayaan 2 was a component of Roskosmos' Luna-Glob moon exploration program. It is possible the Russian agency would collaborate with ISRO in one of its future lunar missions.
Roskosmos Dropout Denial
On January 22, 2013, Physical Research Laboratory (PRL) Director J N Goswami told the press that Chandrayaan 2 would continue to be a joint Indo-Russian project despite the delay.
"The Indo-Russian mission is going ahead. The project has got delayed. Currently, we are whole-heartedly working for the Mars project scheduled for November. The moon mission, for the time being, has got delayed," Goswami told PTI.
"The failure of Roskosmos Phobos-Grunt mission (in December 2011) has, for the time-being, delayed the moon mission," Goswami said, adding the construction of lander for the combined mission has been delayed.
According to PTI, it made repeated attempts to contact S V S Murty, who had announced the Roskosmo drop out a day earlier, but he was not available for comments on the issue.
At a Glance
Launch Date 2015
Launcher GSLV
Total Weight 2,660 kg
Orbiter Weight 1,400 kg
Lander Weight 1,260 kg (35 kg scientific instruments)
Rover 15kg
Launch Schedule
The launch of the spacecraft is scheduled for 2015, but is dependent on the GSLV launcher becoming operational again well in time.
ISRO Chariman K. Radhakrishnan reconfirmed to the press in July 2012 that the Chandrayaan-2 mission could be on its way in 2014. [via The Hindu]
Following the failure of the Russian Phobos-Grunt mission to Mars in November 2011, there were reports in the Russian press that the mission is likely to be rescheduled to 2016.
Academician Lev Zelyony, the director of the Institute for Space Research of the Russian Academy of Sciences told Interfax in February 2012 that "the technical solutions used in the Phobos-Grunt project need to be revised. Those solutions were used for the lunar projects too. It does not touch upon the equipment – it goes about spacecraft and control systems." [via Red Orbit]
However, ISRO's annual report for 2012, released in April 2012, still gives the launch year as 2014
To begin with, the spacecraft was planned to be launched in 2013 (First Quarter) using a GSLV Mk 3. However, following two consecutive failures of the GSLV launcher on April 15, 2010 and December 25, 2010, ISRO has pushed back the launch by nearly two years, and settled on GSLV Mk 1 as the launcher.
The Mk. 1 carries a lighter payload than the Mk 3. As a result, ISRO is limiting the experiments being carried on board.
Speaking to the press on September 9, 2011 ISRO Chairman K Radhakrishnan said, “We have to go through design review and then move ahead”. This mission is slated for 2013-14, he added.
As in early September 2011, ISRO was poised to start developing the engineering model its rover for testing with the lunar surface simulator.
Division of Responsibility
According to Government of India press release on August 4, 2010:
"The Chandrayaan-II project is envisaged to have an Indian Orbiter module with scientific instruments to go round the moon and a Russian Lander module carrying an Indian Rover and a few scientific instruments.
The Chandrayaan-II project will be launched using the Indian Geostationary Launch Vehicle - GSLV. The costs towards these components will be met by the Space Agencies of the respective countries."
ISRO will launch Chandrayaan 2 using a GSLV Mk-2 rocket and realize the orbiter and rover. Roscosmos will realize the lander that will carry the rover to the moon.
Many other countries (USA, France, Germany, Sweden) are expected to participate in the project by contributing instruments and equipment.
During 2009 ISRO and Russian officials talked of there being two rovers. A large main rover designed in Russia and fabricated in India; and a mini-rover designed and fabricated in India, with both rovers being controlled from India.
Following a cost analysis, the Russians gave up on their rover in May 2010.
“The tasks of the mission are to investigate rock samples at the maximum distance from the landing point and to confirm the presence of water,” Roscosmos Deputy Head Anatoly Shilov said at the Bengaluru Space Expo in August 31.
While the Indian rover will analyze lunar surface soil, the Russian lander is likely to drill into the lunar surface and analyse sub surface soil.
Payload Finalization
The payloads for Chandrayaan-2, as recommended by the Advisory Committee on Space Sciences (ADCOS), was announced by ISRO on Monday, August 30, 2010.
ADCOS is chaired by Prof U R Rao and comprises members are drawn from ISRO centres, academic institutions and R and D laboratories and Chaired by Prof U R Rao, Chairman,
"Inclusion of additional payloads, if possible within the mission constraints, will be considered at a later date following a detailed review", ISRO said in a statement
Project Director
The project is being helmed by Dr Mayilsamy Annadurai.
Mission Profile
According to a presentation made by Dr. Goswami and M. Annadurai, project director for Chandrayaan-2, at 2011 Lunar and Planetary Science Conference:
A GSLV Mk-2 launcher will will place the Chandrayaan-2's orbiter, lander and rover, in a transfer orbit around the Earth. From there, the orbiter's onboard rocket engine will propel both the spacecraft and the lander-rover combo into a trajectory that will take them to the Moon.
Once on the lunar transfer trajectory, the orbiter and lander-rover will separate. The two would then journey independently to the Moon,
Landing Sequence
During the landing, the lander's main engine will bring the spacecraft to hover at approximately 2 kms above the lunar surface and then shut down.
The lander will then free fall under the moon's weak gravity, with small thrusters periodically firing to control the rate of descent.
The lander will use a three beam Doppler radar to avoid large obstacles during its descent to the moon's surface.
The accuracy of the autonomous landing system allows the landing area to be predicted as an ellipse that is 30 km long and 15 km wide.
After the lander touches down on the moon, it will release the rover on the lunar surface.
The rover will be equipped with a robotic arm and two instruments to study the chemical composition and volatiles in the lunar surface material within a kilometre of the landing site.
Landing Site
The Chandrayaan-2 lander and rover are both powered with solar panels and hence cannot operate in an area completely devoid of sunlight.
Additionally, the spacecrafts need to be in direct communication with earth for control.
The main scientific goal of the mission is to confirm the presence of water ice on the moon.
It was earlier believed that ice on the moon is confined to areas permanently in darkness. More recent observations suggest ice is also present below the lunar surface in sunlit areas close to the South Pole.
Two candidate landing sites near the Lunar south pole have reportedly been identified by the Russians, based on data from NASA's Lunar Reconnaissance Orbiter (LRO) and Japanese Selena orbiter, which entered lunar orbit in 2007.
The Russian developed Lunar Exploration Neutron Detector, LEND, installed on LRO was used to identify sunlit areas, potentially with sub surface ice. Imagery from Selena and data from LOLA laser altimeter on NASA’s LRO orbiter was used to profile the terrain in these areas.
To begin with 14 sites in sunlight areas close to the South Pole that possibly have subsurface ice were identified..
Nine of these sites were rejected at the outset by the lander team because the terrain was too rough for the landing system of the spacecraft.
Selected Sites
Based on accuracy of the landing system, two sites have been short listed
Main site: 87.2 deg S, 68 deg E, Shoemaker, Faustini
Backup site: 88.5 deg S, 297 deg E, Gerlach
The sites finalized could change if the accuracy of the landing system is improved or based on other data.
Spacecraft Redesign
Once it became clear that Chandrayaan-2 would have to be launched by GSLV and not GSLV-III, the structure configuration of the spacecraft was changed from I2K to I3K to accommodate a revision in payload lift off capacity. The change will facilitate the use of larger propellant
tanks.
The mission strategy was revised to inject the satellite in a lower initial orbit (170 X 16980 km) with a higher lift-off mass of 3200 kg and the Propulsion System Configuration changed to increase fuel carrying capability of the satellite.
Project History
ISRO announced on Wednesday, December 24, 2008, that the design for Chandrayaan II has been completed and it will be launched by 2012.
“The designs for Chandrayaan II have been completed and we hope to launch it by 2012,” ISRO chairperson G. Madhavan Nair told reporters on the sidelines of a function organized by the Confederation of Indian Industry (CII) to felicitate the Chandrayaan I team.
Annadurai told the press on January 18, 2009 that Chandrayaan 2 will be launched using a GSLV Mk III. The complete spacecraft will weigh 2,700 kg.
In a statement to the press on April 20, 2008, following the launch of RISAT 2, TK Alex, director of the ISRO Satellite Center, said that ISRO is finalizing the test equipment that would go with the two rovers that would soft land on the moon.
On August 16, 2009, ISRO chief G Madhavan Nair announced that a joint review of the design with the Russians had been completed.
"Right now, the design has been completed. We had a joint review with Russian scientists here," he said.
"Next...we will go towards prototype building, which will be taken up next year," Nair said.
On November 7, 2009, while inaugurating the sixth National Student Conference at University Visveswaraya College of Engineering, Annadurai stated that the projected will be completed by 2012-13.
“Chadrayaan-II will consist of the spacecraft and a landing platform with two moon rovers, one from India and one from Russia, which will land on the moon and move on wheels on the lunar surface, pick up samples of soil or rocks, do a chemical analysis a nd send the data to the spacecraft orbiting above,’’ Dr Annadurai said.
Design Change Following Discovery of Water on the Moon
Buoyed by the widespread presence of water on the moon, ISRO decided to tweak its Chandrayaan-2 rover payload to facilitate sub-surface soil analysis.
One of the two rovers onboard the Chandrayaan-2 lander will be equipped with a a drill capable of collecting samples from a few millimetres below the lunar surface.
"We have a good head start," said then ISRO chairman G Madhavan Nair.
"The data we have is really exciting and we will definitely have to re-visit the mission objectives.
"We may go for certain midcourse correction of the objectives."
On May 9 2010, Annadurai spoke to The Hindu after delivering the keynote address at the graduation ceremony of B. Tech and MBA students, organised by the Toc-H Institute of Science and Technology (TIST), Arakkunnam, near Cochine.
"The purpose of Chandrayaan-I was to understand what the entire moon contained. But now, the effort would be to understand it in situ. Originally, we wanted to have chemical-mineral analysis, but now that Chandrayaan-I has shown us traces of water on the moon's surface, the emphasis could also be on confirming the finding," he said.
Orbiter
The orbiter will weigh 1,400 kg.
The five payloads recommended for the orbiter by ADCOS are
Large Area Soft X-ray Spectrometer (CLASS) from ISRO Satellite Centre (ISAC), Bangalore and Solar X-ray monitor (XSM) from Physical Research Laboratory (PRL), Ahmedabad for mapping major elements present on the lunar surface.
L and S band Synthetic Aperture Radar (SAR) from Space Applications Centre (SAC), Ahmedabad for probing the first few tens of metres of the lunar surface for the presence of different constituents, including water ice. SAR is expected to provide further evidence confirming the presence of water ice below the shadowed regions of the moon.
Imaging IR Spectrometer (IIRS) from SAC, Ahmedabad for mapping of lunar surface over a wide wavelength range for the study of minerals, water molecules and hydroxyl present.
Neutral Mass Spectrometer (ChACE-2) from Space Physics Laboratory (SPL), Thiruvananthapuram to carry out a detailed study of the lunar exosphere.
Terrain Mapping Camera-2 (TMC-2) from SAC, Ahmedabad for preparing a three-dimensaional map essential for studying the lunar mineralogy and geology.
The orbiter will circle the moon at an altitude of 200 km and is being designed for a life of 2 years.
The other activities completed are: finalization of all electrical and mechanical interfaces including the payload interfaces; Preliminary Design Reviews (PDRs) of Bus Systems (Power, Attitude Orbit
Control Electronics, Telemetry, Tracking and Command Baseband Systems, RF Systems, Data Handling System, Structure, Thermal Control System, Propulsion System); all systems accommodation studies and initial thermal analysis.
Nuclear Powered Orbiter Considered but Dropped
At one stage ISRO contemplated the use of nuclear power for the lunar orbiter in collaboration with Bhaba Atomic Research Center.
"We are thinking of powering some parts of Chandrayaan II with nuclear power and it will power the spacecraft when it revolves around the dark side of the moon," Madhavan Nair, Chairman, ISRO, told media in early August 2009.
Lander / Rovers
The Chandrayaan 2 will comprise a 1,260 kg Russian designed and developed moon lander carrying a single 15 kg rover developed by ISRO in collaboration with Russia.
Lander
The 1,2060 kg Russian lander will carry a scientific payload of 35 kg, not including the rover.
It will be powered by solar panels
It will focus on the geochemical analysis of the lunar soil and the detection of water, which was first confirmed from observations made using Chandrayaan - 1.
Russia is considering the use of a drill that could penetrate as much as a meter below the surface to possibly make contact with water.
Besides equipment to analyse the lunar soil and detect the presence of water, the lander will carry a seismometer and a laser reflector. Also being considered is a landing beacon that could facilitate future landings.
Russia plans to test the lander in 2011, Roscosmos Deputy Head Anatoly Shilov told AW&ST on August 31, 2010
Twin Rovers Considered at One Stage
Early plans envisaged that the moon lander will carry two rovers: A 50 kg Russian rover that will carry the major exploration instruments, and a 15 kg Indian rover, primarily designed to give Indian space scientists experience in robotics and precise remote control over planetary distances, which will separately undertake chemical analysis of the lunar soil.
The 15-kg. (33-lb.), 10-watt, solar-powered Indian rover will include a laser ablation tool for spectral analysis of rocks and soil, and video cameras for navigation. (AW&ST)
Single Rover Finalized
In May 2010, ISRO and Roskosmos dropped plans for a Russian rover, opting for a 15 kg Indian rover..
Rover Details
The rover has been designed in Russia but is being fabricated to Russians specs by Indian scientists.
Using the rover, ISRO scientists hope to hone their deep space communication technology - transmission of commands to the payloads and reception of data collected by them - for future planetary exploration.
Chemical analysis of the lunar soil is a secondary aim of the Indian rover.
Payload
The 15-kg (33-lb) rover will be powered by solar panels. It will carry up to two kilograms of scientific payload. It could be used to collect soil samples and analyse them.
There will be two payloads on the rover for analysis of lunar soil.
Laser induced Breakdown Spectroscope (LIBS) from Laboratory for Electro Optic Systems ( LEOS), Bangalore. (In English, a laser ablation tool for spectral analysis of rocks and soil.)
Alpha Particle Induced X-ray Spectroscope (APIXS) from PRL, Ahmedabad.
Both instruments are expected to carry out elemental analysis of the lunar surface near the landing site.
Rover Development
A significant part of the rover, including its communication package, is being fabricated in Kerala.
On September 10, 2011, ISRO announced that it is ready to start building an engineering test model of the rover for testing with the lunar surface simulator.
Mobility
IIT Kanpur is developing subsystems to provide mobility to the Indian rover to be placed on the moon by the Chandrayaan-2 lander.
The components being developed are: stereophonic camera based 3D vsion, kinematic traction control, and control and motor dynamics of the rover's six wheels.
The 3D vision component is being developed by Dr. K.S. Venkatesh, Associate Professor of Electrical engineering.
3D vision involves generating structured light based 3D map of lunar terrain, Dr Ashish Dutta, Associate Professor of mechanical engineering at IITK told HT:
“As there is no ready made map of the lunar surface, the focus is to use structured light to generate a map of the lunar terrain after landing. Based on the map the robot is expected to move from one point to another for experiments.
Kinematics and path planning involves using the generated map to move to a desired location, choosing the safest path to travel over the lunar terrain which has craters, rocks and dust.
The path chosen should not only be safe but also involve least energy consumption, Dutta said. The system has to factor in moon's lower (1/6th) gravity and the mandate for zero errors.
The stereo vision cameras will provide the ground team controlling the rovers a 3D view of the surrounding terrain.
The rover will have six wheels each driven by an independent electrical motor. Four of the wheels will also be capable of independent steering. A total of 10 electrical motors will be used for traction and steering.
Kinematic traction control will enable the rover to negotiate the rough lunar terrain using independent steering provided on four of its wheels.
IIT Kanpur reported completing the project in March 2012. [via HT]
The developed systems will now be handed over to ISRO for final testing and evaluation.
Rover and Lander Test Center
ISRO is setting up a center in Bangalore for testing of the Chandrayaan-2 rovers and lander, which will have a test area mimicking the lunar terrain and conditions. The Russian rover too will be tested there before being fitted to Chandrayaan-2.
Because of recent speculation that the dense packing of 11 payloads in the Chandrayaan lunar orbiter led to its overheating and subsequent loss, ISRO scientists are less keen to invite payloads from outside space agencies or universities.
Chandrayaan - 2 - Indian Space Projects
