The spacecraft for the Chandrayaan-2 mission will include a rover, a lander that will attempt to touch down near the Moon's south pole, and an orbiter that will travel around the Moon.
What's different this time: The Chandrayaan-2 mission will test whether India's space technology is capable of pulling off a controlled landing (the original mission ended after 10 months when India's Space Organization lost contact with the orbiter). ISRO developed new systems to assist with the soft landing this time around, per Nature.
ISRO's tests in preparation for its second mission mimic the Moon's atmosphere and environment: rovers navigate over rocky surfaces in Bangalore. One of the spacecraft's final tests will begin in three to four weeks.
India's Chandrayaan-2 mission preparing for March 2018 launch
The launch of the next Moon mission could be just four months away. India plans to return to the Moon in a big way with the ambitious Chandrayaan-2, which includes an orbiter, lander, and a small rover. If it all succeeds, it will be India's first soft landing on another world, and only the second such landing since the end of the Apollo and Luna era. For India, landing success would be "a stepping stone for future exploration missions to other planets," according to Indian Space Research Organisation Satellite Centre (ISAC) director M. Annadurai.
The orbiter is a capable one, planned to carry eight instruments into a 100-kilometer, circular, polar lunar orbit, following on the work of India's previous orbiter, Chandrayaan-1. It has a nominal mission lifetime of one year. The lander and rover payloads are more limited, as befits the first demonstration of a soft lander. The lander and rover have nominal lifetimes of one lunar daytime (14 Earth days). I was unable to find any information on whether there is any possibility that the lander or rover could wake up again after the long lunar night, as China's Chang'e 3 lander has done for years. It's enough to hope that India can follow its first and only lunar orbiter with its first lunar lander.
Chandrayaan-2 is planned to launch in March from ISRO's Sriharikota launch center aboard a Geosynchronous Satellite Launch Vehicle Mark 2 (GSLV Mk 2) rocket, making it ISRO's first deep-space launch on its newer, heavier launch vehicle. The combined mass of the three component spacecraft is 3250 kilograms, dramatically larger than the approximately 1300-kilogram mass of both Chandrayaan-1 and Mars Orbiter Mission, both of which launched on smaller Polar Satellite Launch Vehicles (PSLVs). (For fun, you can download and build a paper model of the GSLV Mk 2 spacecraft here.)
The GSLV will place Chandrayaan-2 into an elliptical Earth parking orbit, enlarging it over days or weeks with periapsis burns to raise the orbit apogee. Eventually, the apogee will be high enough that a burn can send the spacecraft on to a lunar transfer trajectory. A lunar orbit insertion burn will place Chandrayaan-2 into an elliptical orbit and the spacecraft will begin braking at periapsis to reduce its orbit to a 100-kilometer circle. I haven't found a reference that says how long this process is expected to take from launch to final orbit, but a similar process took Chandrayaan-1 three weeks, from October 22 to November 12, 2008.
CHANDRAYAAN-2 LAUNCH, LUNAR TRANSFER, AND LANDING TRAJECTORY
Modified from a presentation given by ISRO director M. Annadurai to the United Nations Committee on the Peaceful Uses of Outer Space in June 2017.
Once the spacecraft is in its science orbit at the Moon, the lander mission can begin. While the orbiter doesn't care much about what phase the Moon is in, the lander and rover need sunlight for warmth and power, so the timing of launch will be dictated by the necessity to get the lander on the ground at its landing site very soon after local dawn. However, the concept of dawn is a bit tricky, because the landing site is planned to be near the south pole. I haven't seen any recent information on the specific landing site choice. As of 2012, an earlier concept that involved Russian collaboration had proposed landing sites that were quite near the South Pole indeed, at 87.2 and 88.5 degrees south.
The landing will happen entirely autonomously. The lander will separate from the orbiter and immediately perform a deboost maneuver, changing its orbit around the Moon to one with an 18-kilometer periapsis. When it reaches periapsis, the lander will begin the "rough braking phase," braking to reduce its orbit altitude to 7 kilometers.
At an altitude of 7 kilometers, the lander will use a camera to take photos of the lunar surface and determine its relative position and velocity compared to its onboard map of the landing region. The lander will autonomously determine the trajectory necessary to bring it to its desired landing site, and steer itself to a location 100 meters above the site, where it will come to a hover. It will use a hazard avoidance sensor to map the surface for potential hazards and select a safe location for touchdown. The lander will slowly descend until it reaches 2 meters above that location. Then it will cut its engines. The lander will fall to the surface, its four lander legs absorbing the shock of landing. The rover will roll out of the lander shortly after the landing in order to make the most of its brief, two-week primary mission.
CHANDRAYAAN-2 LANDING TRAJECTORY
From M. Annadurai et al. presentation to the 10th IAA Symposium on the Future of Space Exploration, Torino, Italy, 27-29 June, 2017.
The orbiter is physically similar to Chandrayaan-1. It is three-axis stabilized with reaction wheels. The orbiter carries five science instruments and two supporting instruments.
- Terrain Mapping Camera 2 (TMC-2) is based upon TMC (a predecessor on Chandrayaan-1) and will perform 3D mapping of the lunar surface using two cameras.
- Collimated Large Array Soft X-ray Spectrometer (CLASS) is based upon C1XS (a predecessor on Chandrayaan-1) and will map abundance of major rock-forming elements on the Moon including Mg, Al, Si, Ca, Ti, and Fe. Assisting it is the Solar X-ray Monitor (XSM), which measures solar x-ray emission.
- Chandra's Atmospheric Composition Explorer(ChACE-2) is a neutral mass spectrometer that is based upon CHACE (a predecessor on Chandrayaan-1's Moon Impact Probe).
- Synthetic Aperture Radar (SAR) will perform radar mapping of the surface in both L and S bands of the radio spectrum. It has heritage from MiniSAR on Chandrayaan-1 but will be the first L-band radar mapper to orbit the Moon.
- Imaging Infra-Red Spectrometer (IIRS) is sensitive to light with wavelengths between 0.8 and 5 microns and has the specific goal of mapping the abundance of hydroxl ions and molecular water.
- Finally, the Orbiter High Resolution Camera (OHRC) will perform high-resolution imaging of the landing site prior to the lander mission.
CAD MODEL OF CHANDRAYAAN-2, LAUNCH CONFIGURATION
Chandrayaan-2 consists of an orbiter, lander, and small rover. Here, the spacecraft is shown in its launch configuration.
Physically, the lander is shaped like a truncated square-based pyramid, built around a cylinder that houses the substantial propellant tank. It will perform inertial navigation throughout the descent using its Laser-gyro-based inertial reference unit and accelerometer package, LIRAP. The propulsion system includes four throttleable engines that can each provide 800 newtons of thrust, and 8 attitude rockets of 50 newtons each. The lander will communicate direct to Earth using a steerable, dual-gimbal, S-band radio antenna.
The lander has multiple cameras in its Hazard Detection and Avoidance (HDA) system, which it will use to determine horizontal velocity from feature tracking and identify the landing site using pattern matching. HDA also contains microwave and laser altimeters and a laser Doppler velocimiter. The HDA system collects data and instructs the rockets to fire to steer the lander to the landing site. I didn't find any reference that indicated whether the lander has the ability to photograph the landscape it's sitting on. Surely it must, but I don't know.
Once on the ground, the lander will deploy its science payload:
- Instrument for Lunar Seismic Activity (ILSA) will study moonquakes. Large enough quakes could allow it to study the Moon's deep interior, potentially from a polar position not accessible to the Apollo seismometers, which would be cool. This experiment will be a lot cooler if the lander is capable of surviving multiple lunar days.
- Chandra’s Surface Thermophysical Experiment (ChaSTE) will measure thermal properties of the lunar surface.
- Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere (RAMBHA-Langmuir Probe) will measure near surface plasma density and how it changes over the course of the lunar daytime. According to a recent Nature article, lunar plasma is thought to participate in the levitation of lunar dust, a problem for future human exploration.
And, of course, the lander will carry a rover. The rover is very small, roughly Sojourner-sized, at 20 kilograms. Like NASA's Mars rovers, the Chandrayaan-2 rover uses a rocker-bogie suspension system supporting six independently motorized wheels, but unlike NASA's rovers its corner wheels do not steer. Therefore, it steers by rotating the wheels at different rates, like a tank. This is a perfectly fine method for a lightweight rover as long as the net effect of steering isn't to sink the rover into the soil.
To make sure the rover could move and steer on the Moon without embedding, ISRO developed a big sandbox filled with crushed anorthosite to test rover mobility in. When NASA does this with Mars rovers, they build full-size mobility system mockups with tiny bodies so the whole vehicle weighs on Earth what the real rover weighs on Mars, where gravity is a third of Earth's. But that wouldn't work for the already-small Chandrayaan-2 rover trying to simulate lunar gravity at a sixth of Earth's. So ISRO developed a different solution that I just love: attaching a giant helium-filled balloon to a duplicate test rover to counterbalance 5/6 of its weight. These tests succeeded, evidently.
MOBILITY TESTING OF THE CHANDRAYAAN-2 ROVER
ISRO employs a balloon to counteract 5/6 of the weight of a duplicate of the Chandrayaan-2 rover in order to test its mobility on simulated lunar soil at lunar gravity. From M. Annadurai et al. presentation to the 10th IAA Symposium on the Future of Space Exploration, Torino, Italy, 27-29 June, 2017.
Because of its small size, the rover instrumentation is fairly limited, much like Sojourner's was. It has two navigation cameras for stereo path planning and an inclinometer for safety (drives will stop if the rover's inclination or motor current gets too high). It has no rear-facing cameras. It will use a small radio antenna for communication with the lander, which will relay rover data to Earth. The radio antenna is atop its vertically-mounted solar panel. Its solar panel is mounted vertically because of the near-polar landing site. That suggests the rover will need to turn in place after traverses to align the panel for good power production.
The rover is equipped with two science instruments for elemental composition, both of which point downward, beneath the rover: a Laser-Induced Breakdown Spectroscope (LIBS) and an Alpha Particle X-Ray Spectrometer. In general, LIBS will get you lower-mass elements and APXS will get you higher-mass elements, with substantial overlap between them. LIBS is faster, APXS more sensitive to trace elements if you can give it long enough integration time. Perhaps they will be using LIBS along traverses, and APXS at stops.
Interestingly, a paper I read about the LIBS instrument suggested it was designed for a one-year primary mission. Officially, the lander mission has an expected lifetime of 14 days, but maybe there is hope that it will survive a lunar night to do science on a second lunar day. That would be awesome. But any successful landing at all would be an enormous accomplishment for India; I don't want to get greedy.
Originally, Chandrayaan-2 was supposed to be a collaboration with the Russian space agency, but budget problems made Russia drop out, and India decided to go it alone. If Chandrayaan-2 succeeds, India's next step will be lunar sample return. They'd be following exactly the same path China has at the Moon, going quickly from a successful orbiter, to a lander/rover, to autonomous sample return. Unlike China, however, India is using international collaboration to increase its chances for success; Indian prime minister Narendra Modi and his Japanese counterpart Shinzo Abe signed an agreement a couple of weeks ago to collaborate on a future joint lunar sample return mission.
A lot of people are trying to make the separate Chinese and Japanese/Indian lunar efforts into a race. To be sure, there is some national pride riding on successes in space, and reaching milestones first. But races have only one winner. We all win when more organizations launch scientific missions into space. All of these countries have shared the data they gathered during past missions with scientists and the public. India's mission landing near the south pole, and China's landing on farside, will only enhance global understanding of the Moon, regardless of who gets there first. India or China may yet be defeated by physics -- deep-space exploration is challenging -- but they won't be defeated by each other's success.
Good luck, saubhaagy to ISRO and India on the upcoming launch of Chandrayaan-2!
Many thanks to Sriram Bhiravarasu for providing me some papers I used as sources for this article.
Annadurai M (2017) "Future Exploration Missions of ISRO" presentation to the 60th session of the United Nations Committee on Peaceful Exploration of Outer Space, 7-16 June 2017, Vienna, Austria
Annadurai M et al (2017) "Chandrayaan-2 lunar orbiter & lander mission" abstract presented to the 10th IAA Symposium on the Future of Space Exploration: Towards the Moon Village and Beyond, 27-29 June 2017, Torino, Italy
Quelle: The Planetary Society
Isro’s 2nd Moon mission set for March-April 2018
‘Chandrayaan-II’ would be launched during March-April 2018, by using a Geosynchronous Satellite launch vehicle.
Chandrayaan-II’ would be launched during March-April 2018, by using a Geosynchronous Satellite launch vehicle.
The country’s second mission to the Moon, ‘Chandrayaan-II’ would be launched during March-April 2018, by using a Geosynchronous Satellite launch vehicle (GSLV MK II). This prestigious mission will include a lunar, Orbiter, lander and rover, said Dr. Mylswamy Annadurai, director, ISRO Satellite Centre, Bengaluru.
Addressing a press conference at Tiruchy on Saturday, he said that they were preparing three unmanned vehicles for the mission developed in India including an orbiter craft, to hover above the moon’s surface, a rover, and a lander to facilitate the landing of the rover safely on the moon. This lunar mission will use and test various new technologies and conduct further experiments. The wheeled rover will move on the lunar surface and will perform a chemical analysis on site, he said.
Dr Annadurai said the orbiter will orbit the moon at an attitude of 100-km and create a detailed three-dimensional map of the lunar surface. The mission will carry five instruments on the orbiter namely, a large area soft X-ray spectrometer for mapping significant elements there on the lunar surface, L and S band synthetic aperture radar for probing the first few tens of metres on the surface of the moon for presence of constituents like water.
Quelle: Deccan Chronicle
Chandrayaan-2 mission on schedule: ISRO...
India plans tricky and unprecedented landing near moon’s south pole
A model of Chandrayaan-2’s rover undergoing tests to prepare for operating in the moon’s anemic gravity.
BENGALURU, INDIA—Sometime this summer, a spacecraft orbiting over the moon's far side, out of contact with controllers on Earth, will release a lander. The craft will ease to a soft landing just after lunar sunrise on an ancient, table-flat plain about 600 kilometers from the south pole. There, it will unleash a rover into territory never before explored at the surface; all previous lunar craft have set down near the equator.
That's the ambitious vision for India's second voyage to the moon in a decade, due to launch in the coming weeks. If Chandrayaan-2 is successful, it will pave the way for even more ambitious Indian missions, such as landings on Mars and an asteroid, as well a Venus probe, says Kailasavadivoo Sivan, chairman of the Indian Space Research Organisation (ISRO) here. Chandrayaan-2, he says, is meant to show that India has the technological prowess "to soft land on other heavenly bodies."
But lunar scientists have much at stake, too. "There has been a rebirth of lunar exploration across the globe, and India can't be left behind," says Mylswamy Annadurai, director of the ISRO Satellite Centre. Instruments aboard the lander and rover will collect data on the moon's thin envelope of plasma, as well as isotopes such as helium-3, a potential fuel for future fusion energy reactors. The orbiter itself will follow up on a stunning discovery by India's first lunar foray, the Chandrayaan-1 orbiter, which found water molecules on the moon in 2009. Before that, "It was kind of a kooky science to think that you'd find water" there, says James Greenwood, a cosmochemist at Wesleyan University in Middletown, Connecticut. "Now, we're arguing about how much water, and not whether it has water or not." Cameras and a spectrometer aboard the Chandrayaan-2 orbiter could help settle that question.
India Prepares For Second Lunar Mission with Chandrayaan-2
India's space agency, the Indian Space Research Organization (ISRO), is prepping for its second mission to the moon, which is scheduled for blast off around April 2018.
The objective for the venture is to explore the lunar south pole.
Dubbed Chandrayaan-2, the spacecraft is expected to take an estimated one to two months to reach lunar orbit. Once the craft is in position, a lander will then detach itself and navigate toward the Earth's moon. After touching down on the rocky surface, a rover will depart the lander and begin its exploration of the southern region.
"Chandrayaan-2 is a challenging mission as for the first time we will carry an orbiter, a lander and a rover to the moon," K. Sivan, chairman of the ISRO, told the Times of India.
"The rover has been designed in such a way that it will have power to spend a lunar day or 14 Earth days on the moon's surface and walk up to 150-200 metres. It will do several experiments and on-site chemical analysis of the surface."
"The rover will then send data and images of the lunar surface back to the Earth through the orbiter within 15 minutes," the chairman added.
Since the rover can only store up to 14 days' worth of power, Sivan indicated that until it is able to collect enough sunlight and recharge itself, it will remain in sleep mode.
"We are hoping the rover will again come alive whenever that part of the moon gets sunlight and recharges the rover's solar cells," Sivan said.
"Besides the rover, the orbiter will also capture images of the moon while orbiting it."
When asked about a more concrete launch date, Sivan told the publication that it depends on several different factors.
"All three components of the lunar module are almost ready. Currently, their integration is going on," he said.
"Once the module is ready, it will have to go through rigorous tests. The launch date will depend on various factors like the moon's relative position with respect to the Earth."
The spacecraft, which will be launched using a Geostationary Satellite Launch Vehicle Mark II rocket, is set to take off from the Satish Dhawan Space Center in Sriharikota, in the southeastern state of Andhra Pradesh.
Prior to the Chandrayaan-2, the agency launched the Chandrayaan-1 in October 2008. Though the mission was expected to last for two years, it only lasted roughly 10 months after the orbiter stopped communicating with the station in August 2009.