We can all breathe easy, as ISRO has successfully launched the Chandrayaan 2 mission to moon, a monumental achievement in the space agency's history.
It's the first time we're landing a spacecraft on the moon, on its unexplored south pole region. In order to do that of course, they first had to simulate a lunar environment to test their hardware.
Images courtesy: ISRO
Specifically, ISRO needed an environment to test the Vikram moon lander and the Pragyaan rover. The plan, when the mission reaches the moon, is for Vikram to detach from the lunar orbiter and make a soft-landing on the Moon's surface. It will then open up and release the rover (housed inside it) which will explore and carry out surface experiments.
"The surface of the earth and that of the moon are entirely different. So we had to create an artificial moon surface and test our rover and lander," M Annadurai, who retired as Director of the UR Rao Satellite Centre (URSC), told IANS.
The moon's surface is covered with craters, rocks, dust, and soil, all of a different texture compared to that of Earth. ISRO scientists needed to be absolutely sure that wouldn't cause their rover's wheels or legs to malfunctions, and that the lander would be able to touch down safely.?
Since importing the right kind of soil from the US would be too expensive, ISRO began looking for a local solution. After all, it needed about 60 to 70 metric tons of soil, and a shoestring budget to get it within. So geologists began suggesting the space agency source material from near Salem in Tamil Nadu. This region is full of "anorthosite" rock, soil from which is similar to that on the surface of the Moon.
ISRO did eventually source rocks from the area in Tamil Nadu, with Annadurai saying they were crushed as needed and moved to the Lunar Terrain Test Facility in Bengaluru.
The Pragyaan rover on the ramp up to the storage bay of the Vikram lander
"A sum of Rs 25 crore was budgeted for the purpose but it came down drastically as the service providers did not charge us," Annadurai said.
"Initially the rover was of four-wheel configuration. But we changed to six-wheel configuration after experiments to give it more stability. Some changes were made to the wheel size as well," he added.
He also said helium balloons were attached to the rover during testing in order to simulate the lowered weight of the rover in the Moon's microgravity.
The lander meanwhile was tested at ISRO's facility at Challakere in the Chitradurga district of Karnataka. The space agency created artificial craters at the site, similar to where Vikram is expected to set down. It will of course use its onboard sensors to scan the lunar terrain before landing, to see if it's safe enough. If necessary it will move to another nearby spot to set down, but the lander still needs to be as stable as possible to avoid a critical failure
"We put the sensors in the small plane belonging to NRSC (National Remote Sensing Centre) and flew it over the test bed couple of times to check the sensors as to whether it can read the terrain properly," Annadurai said. ISRO also tested the actuators and thrusters on the lander, to ensure it can safely touch down.
An illustration of the Pragyaan rover scooting across the lunar surface
The landing itself has to be exactly right. Firing the lander's thrusters too close to the surface could cause a backflow of moon dust, including jagged particles. Not only could this potentially, damage the lander, but the dust could also end up sticking to and coating things like its sensors and solar panels, disrupting the mission. So instead, ISRO had to practice a precise sort of braking procedure, relying on the lowered weight in microgravity for the lander to slowly free fall the last few feet.
Essentially, there was a lot more work to do after the actual hardware was built. Now let's just hope the modules being put onto (and above) the moon manage to do their jobs without a hitch as they finally descend on to the moon's surface in early September.