Peter Lobner, updated 2 December 2019

After the failure of Israel’s Beresheet spacecraft to execute a soft landing on the Moon in April 2019, India is the next new contender for lunar soft landing honors with their Chandrayaan-2 spacecraft.  We’ll take a look at the Chandrayaan-2 mission in this post.

If you’re not familiar with the Israel’s Beresheet lunar mission, see my 4 April 2019 post at the following link:  https://lynceans.org/all-posts/israel-is-poised-to-become-the-4th-nation-to-land-a-spacecraft-on-the-moon/

1. Background:  India’s Chandrayaan-1 mission to the Moon

India’s first mission to the Moon, Chandrayaan-1, was a mapping mission designed to operate in a circular (selenocentric) polar orbit at an altitude of 100 km (62 mi).  The Chandrayaan-1 spacecraft, which had an initial mass of 1,380 kg (3,040 lb), consisted of two modules, an orbiter and a Moon Impact Probe (MIP). Chandrayaan-1 carried 11 scientific instruments for chemical, mineralogical and photo-geologic mapping of the Moon.  The spacecraft was built in India by the Indian Space Research Organization (ISRO), and included instruments from the USA, UK, Germany, Sweden and Bulgaria.  

Chandrayaan-1 was launched on 22 October 2008 from the Satish Dhawan Space Center (SDSC) in Sriharikota on an “extended” version of the indigenous Polar Satellite Launch Vehicle designated PSLV-XL. Initially, the spacecraft was placed into a highly elliptical geostationary transfer orbit (GTO), and was sent to the Moon in a series of orbit-increasing maneuvers around the Earth over a period of 21 days.  A lunar transfer maneuver enabled the Chandrayaan-1 spacecraft to be captured by lunar gravity and then maneuvered to the intended lunar mapping orbit.   This is similar to the five-week orbital transfer process used by Israel’s Bersheet lunar spacecraft to move from an initial GTO to a lunar circular orbit.

The goal of MIP was to make detailed measurements during descent using three instruments: a radar altimeter, a visible imaging camera, and a mass spectrometer known as Chandra’s Altitudinal Composition Explorer (CHACE), which directly sampled the Moon’s tenuous gaseous atmosphere throughout the descent.  On 14 November 2008, the 34 kg (75 lb) MIP separated from the orbiter and descended for 25 minutes while transmitting data back to the orbiter.  MIP’s mission ended with the expected hard landing in the South Pole region near Shackelton crater at 85 degrees south latitude.

In May 2009, controllers raised the orbit to 200 km (124 miles) and the orbiter mission continued until 28 August 2009, when communications with Earth ground stations were lost.  The spacecraft was “found” in 2017 by NASA ground-based radar, still in its 200 km orbit.

Numerous reports have been published describing the detection by the Chandrayaan-1 mission of water in the top layers of the lunar regolith.  The data from CHACE produced a lunar atmosphere profile from orbit down to the surface, and may have detected trace quantities of water in the atmosphere.  You’ll find more information on the Chandrayaan-1 mission at the following links:

• NASA website, “Chandrayaan-1 / Moon Impact Probe;”  https://solarsystem.nasa.gov/missions/chandrayaan-1/in-depth/

• Space.com website: “Chandrayaan-1: India’s First Mission to the Moon;”  https://www.space.com/40114-chandrayaan-1.html

• The Planetary Society website, “Water on the Moon: Direct evidence from Chandrayaan-1’s Moon Impact Probe;” http://www.planetary.org/blogs/emily-lakdawalla/2010/2430.html

2. India’s upcoming Chandrayaan-2 mission to the Moon

Chandrayaan-2 was launched on 22 July 2019.  After achieving a 100 km (62 mile) circular polar orbit around the Moon, a lander module will separate from the orbiting spacecraft and descend to the lunar surface for a soft landing, which currently is expected to occur in September 2019, after a seven-week journey to the Moon.  The target landing area is in the Moon’s southern polar region, where no lunar lander has operated before.  A small rover vehicle will be deployed from the lander to conduct a 14-day mission on the lunar surface.  The orbiting spacecraft is designed to conduct a one-year mapping mission.

The launch vehicle

India will launch Chandrayaan-2 using the medium-lift Geosynchronous Satellite Launch Vehicle Mark III (GSLV Mk III) developed and manufactured by ISRO.  As its name implies, GSLV Mk III was developed primarily to launch communication satellites into geostationary orbit.  Variants of this launch vehicle also are used for science missions and a human-rated version is being developed to serve as the launch vehicle for the Indian Human Spaceflight Program.

The GSLV III launch vehicle will place the Chandrayaan-2 spacecraft into an elliptical parking orbit (EPO) from which the spacecraft will execute orbital transfer maneuvers comparable to those successfully executed by Chandrayaan-1 on its way to lunar orbit in 2008.  The Chandrayaan-2 mission profile is shown in the following graphic. You’ll find more information on the GSLV Mk III on the ISRO website at the following link:  https://www.isro.gov.in/launchers/gslv-mk-iii

The spacecraft

Chandrayaan-2 builds on the design and operating experience from the previous Chandrayaan-1 mission.  The new spacecraft developed by ISRO has an initial mass of 3,877 kg (8,547 lb).  It consists of three modules: an Orbiter Craft (OC) module, the Vikram Lander Craft (LC) module, and the small Pragyan rover vehicle, which is carried by the LC.  The three modules are shown in the following diagram.

Chandrayaan-2 carries 13 Indian payloads — eight on the orbiter, three on the lander and two on the rover. In addition, the lander carries a passive Laser Retroreflector Array (LRA) provided by NASA. 

The OC and the LC are stacked together within the payload fairing of the launch vehicle and remain stacked until the LC separates in lunar orbit and starts its descent to the lunar surface.

The solar-powered orbiter is designed for a one-year mission to map lunar surface characteristics (chemical, mineralogical, topographical), probe the lunar surface for water ice, and map the lunar exosphere using the CHACE-2 mass spectrometer.  The orbiter also will relay communication between Earth and Vikram lander.

The solar-powered Vikram lander weighs 1,471 kg (3,243 lb).  The scientific instruments on the lander will measure lunar seismicity, measure thermal properties of the lunar regolith in the polar region, and measure near-surface plasma density and its changes with time. 

The 27 kg (59.5 lb) six-wheeled Pragyan rover, whose name means “wisdom” in Sanskrit, is solar-powered and capable of traveling up to 500 meters (1,640 feet) on the lunar surface. The rover can communicate only with the Vikram lander.  It is designed for a 14-day mission on the lunar surface.  It is equipped with cameras and two spectroscopes to study the elemental composition of lunar soil.

You’ll find more information on the spacecraft in the 2018 article by V. Sundararajan, “Overview and Technical Architecture of India’s Chandrayaan-2 Mission to the Moon,” at the following link:

http://epizodsspace.airbase.ru/bibl/inostr-yazyki/Chandrayaan-2.pdf

Also see the ISRO webpage for the GSLV-Mk III – M1 / Chandrayaan-2 mission at the following link:

https://www.isro.gov.in/launcher/gslv-mk-iii-m1-chandrayaan-2-mission

Best wishes to the Chandrayaan-2 mission team for a successful soft lunar landing and long-term lunar mapping mission.

Update 2 December 2019: Vikram lander crashed on the Moon

After a 48-day transit following launch, and an apparently nominal descent toward the lunar surface, communications with the Vikram lander were lost on 6 September 2019, when the spacecraft was at an altitude of about 2 km (1.2 miles), with just seconds remaining before the planned landing. Communications with the Chandrayaan orbiter continued after communications was lost with the Vikram lander. More details on India’s failed landing attempt are in the 25 November 2019 article on the Space.com website here: https://www.space.com/india-admits-moon-lander-crash.html

In December 2019, NASA reported finding the Vikram impact site in photos taken by the Lunar Reconnaissance Orbiter spacecraft. Details are at the following NASA link: https://www.nasa.gov/image-feature/goddard/2019/vikram-lander-found