ISRO launches India’s first lunar landing mission

by Chris Gebhardt

In a historic move, the Indian Space Research Organisation (ISRO) has launched the Chandrayaan-2 mission to the Moon – a group of three spacecraft that will orbit, land, and rove the lunar surface. 

If the landing is successful, India will become only the fourth nation to soft land on the Moon, following the Soviet Union, the United States, and China.

After a scrub less than an hour before the launch attempt on Sunday, 14 July, ISRO launched the mission on Monday, July 22 at 14:43 Indian Standard Time, which is 09:13 UTC (05:13 EDT) that same day.

History, launch, and 54-day flight to the Moon:

The fact that India’s first soft lunar landing mission’s launch will coincide within a day of the 50th anniversary of the Apollo 11 lunar landing is completely coincidental.

The mission was originally targeted to launch in 2011 as a joint Indian-Russian venture, with the Russian Federal Space Agency, Roscosmos, providing the lunar Lander while the Indian Space Research Organisation (ISRO) provided the Orbiter and the Rover.

Natural delays in design and build, as well as Roscosmos’ financial difficulties, delayed the mission to 2013.  Then, the November 2011 mission failure of the Phobos-Grunt Mars probe delayed construction of Russia’s Lander contribution and pushed the Chandrayaan-2 mission into 2015.

Continued financial fallout from the Phobos-Grunt mission failure as well as other financial problems plaguing Roscosmos eventually led the Russian agency to withdraw from the Chandrayaan-2 mission.

India then decided to do the mission by itself.  With that, the launch was pushed to March 2018 before incurring delays to April and October of that same year before moving into the “first half of 2019”. 

Minor damage to two of the Lander’s legs during pre-flight testing in February 2019 further delayed the launch to 14 July.

After launch, Chandrayaan-2 will employ a slow outward spiral trajectory to the Moon, performing a series of burns to progressively raise its apogee – farthest point in orbit from the Earth – to eventually intercept the Moon 30 days after launch.

The historic flight will launch on the Geosynchronous Satellite Launch Vehicle Mark 3, or GSLV Mk-III for short, from the Second Pad at the Satish Dhawan Space Centre in India

The stacked configuration of Chandrayaan-2 for launch and its outward journey to the Moon. The Rover is inside the Lander. (Credit: ISRO)

The GSLV Mk-III is a three-stage, medium lift rocket designed primarily for inserting satellites into geostationary orbit.

The most powerful rocket in ISRO’s arsenal, it was the prime candidate for the Chandrayaan-2 mission and will also be the vehicle to launch humans into space as part of the Indian Human Spaceflight Programme.

Standing 43.4 m (142 ft) tall, the 640,000 kg (1.4 million lb) vehicle employs two, large, side-mounted solid rocket boosters as its first stage before transitioning to liquid fueled 2nd and 3rd stages for final Earth orbit insertion.

Chandrayaan-2’s updated launch sequence for 22 July is: 

Mission Elapsed Time Event Altitude
0 seconds Booster ignition / Liftoff 0 km
110.84 seconds L110 Second Stage ignition 43.939 km
131.3 seconds Solid rocket separation 61.995 km
203.94 seconds Payload fairing separation 114.511 km
305.72 seconds L110 second stage shutdown 169.079 km
308.82 seconds L110 second stage separation 170.783 km
311.22 seconds C25 third stage ignition 172.072 km
959.3 seconds C25 third stage shutdown 176.415 km
974.3 seconds Chandrayaan-2 separation 181.656 km

During launch, the twin S200 solid rocket boosters provided 10,300 kilonewtons (kN) of thrust (2,315,532 lbf), the L110 second stage’s two Vikas liquid-fueled engines imparted a total of 1,598 kN (359,244.7 lbf) of thrust, and the C25 third stage’s single C20 engine provided 200 kN (44,961.8 lbf) of thrust.

At Earth orbit insertion, Chandrayaan-2 will be in a highly elliptical 181.6 x 39,120 km (112.8 x 24,308.04 mile) orbit.

Updated Chandrayaan-2 mission timeline for a launch on 22 July. (Credit: ISRO)

Immediately, ISRO will perform a series of powerups and checkouts of the Chandrayaan-2 Orbiter/Lander/Rover stack to confirm the health of the spacecraft before it begins a series of apogee raising maneuvers to increase its farthest distance from Earth during each orbit.

In other words, Chandrayaan-2 will gradually spiral its farthest point from Earth farther away from our planet via a series of orbit raising maneuvers performed at each orbital perigee – closest approach to Earth in an orbit – by the Chandrayaan-2 Orbiter’s main engine. 

This orbital apogee raising process will now take 23 days (opposed to the original 17 days for a launch on 14 July), after which Chandrayaan-2 will be in the perfect position at orbital perigee to fire the Orbiter’s main engine again, this time performing the Trans-Lunar Injection (TLI) burn to send the spacecraft to the Moon.

The TLI burn will place Chandrayaan-2’s orbital apogee at lunar distance at a precise point so it will intercept the Moon 7 days later – 2 days longer than originally planned.

Upon lunar intercept 30 days after launch, Chandrayaan-2 will use the Orbiter’s main engine to perform the Lunar Orbit Insertion burn to shift its orbit from the Earth to the Moon.

The spacecraft stack will then spend the next 13 days (opposed to 28 days per the original timeline) firing the Orbiter’s main engine periodically to change the highly elliptical lunar capture orbit to a circular 100 x 100 km (62 x 62 mile) lunar orbit.

Once in its lunar science orbit, the Lander (with Rover inside) will separate from the Orbiter 43 days after launch (instead of 50 days).  The following day, the Lander will begin its 4-day descent to the lunar surface.

The Lander’s touch down on the southern polar region of the Moon is slated to occur 48 days after launch (opposed to 54 days per the original plan).

The components of Chandrayaan-2:

The Chandrayaan-2 mission is comprised of three primary components: an Orbiter, a Lander, and a Rover.

The Orbiter:

The Orbiter part of the mission is the only element that does not carry a specific name and is instead referred to solely as the Chandrayaan-2 Orbiter.

Serving as a science platform in its own right as well as a telecommunications relay between the Lander that will be deployed on the lunar surface, the Chandrayaan-2 Orbiter will communicate directly with the Indian Deep Space Network at Bayalalu.

The Orbiter. (Credit: ISRO)

Weighing in at 2,379 kg (5,244.7 lb), it carries a 1,000 W electric power generation capability and a mission lifetime of one Earth year.

In all, the Orbiter carries eight scientific experiments, including: the Terrain Mapping Camera 2, the Chandrayaan 2 Large Area Soft X-ray Spectrometer, the Solar X-ray Monitor, the Orbiter High Resolution Camera, the Imaging IR Spectrometer, Dual Frequency Synthetic Aperture Radar, the Chandrayaan 2 Atmospheric Composition Explorer 2, and Dual Frequency Radio Science.

The Lander:

The first element of the mission to bear a name of its own, the Lander is called Vikram after Dr. Vikram A. Sarabhai, considered the Father of the Indian Space Programme.

Vikram weighs 1,444 kg (3,183.4 lb) – with the Rover inside, that increases to 1,471 kg (3,243 lb) – and is capable of generating 650 W of electric power via the use of two side mounted solar panels.

The Lander is designed to function for a single lunar day, 14 Earth days, and is capable of communicating directly with the Indian Deep Space Network, the Chandrayaan-2 Orbiter, and the Rover on the lunar surface.

Vikram is equipped with eight 50 N (11 lbf) thrusters for attitude control and five 800 N (180 lbf) liquid fueled main engines.

To aid with its landing, Vikram carries a high-resolution camera, a navigation camera, a hazard avoidance camera, an altimeter, a velocity meter, and the associated software to integrate these components.

Extensive testing was performed in rural parts of India to ensure the Lander’s systems could safely detect any hazards that go unnoticed via observations of the landing site by the high resolution camera on the Orbiter prior to landing.

Vikram is also designed to safely land on slopes of up to 12°.

The five 800 N engines will allow Vikram to slowly ease onto the lunar surface at a speed of just 2 meters per second (6.5 feet per second).

Vikram itself, in addition to serving as a communications relay between the Rover and the Orbiter/India, carries three scientific experiments of its own, including the Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere instrument, the Chandra’s Surface Thermo-physical Experiment, and the Instrument for Lunar Seismic Activity experiment.

Vikram also carries, inside of it, the Rover that will be deployed to the lunar surface.

The Vikram lander. (Credit: ISRO)

Following landing, a door on the side of Vikram will open and extend down to the lunar surface, providing a ramp for the Rover.

For launch, cruise to the Moon, and landing, the Rover will be attached to the door and then deployed down with it.

After the door is fully deployed, a solar panel on the Rover will be extended and the Rover activated before it rolls itself down onto the lunar surface.

The Rover:

The 27 kg (59.5 lb), six-wheeled Rover will be India’s first roving robotic explorer on another celestial body.

The Rover’s single, extendable solar panel will generate 50 W of electric energy for the vehicle.

Named Pragyan – “wisdom” in Sanskrit – the Rover can travel up to half a kilometer, or 500 m (1,640 ft), and will function for a single lunar day, 14 Earth days.

The Pragyan rover. (Credit: ISRO)

It is only capable of communicating with the Vikram lander, and therefore all of its scientific and data results will have to be relayed through the Lander back to either the Orbiter or directly to Earth.

Its maximum speed is 1 cm per second (0.03 ft per second).

Pragyan carries two science experiments, the Alpha Particle X-ray Spectrometer and the Laser Induced Breakdown Spectroscope.

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