BENGALURU: On a day India’s solar satellite began its 1.5 million-km journey, the country’s lunar mission achieved all its objectives, paving the way for Isro to put the Chandrayaan-3 lander (Vikram) and rover (Pragyan) to sleep on Sunday.
Sunday, which is the 12th day since India achieved the historic soft-landing on the lunar surface, will see both Vikram and Pragyan retire for the night, Chandrayaan-3 project director P Veeramuthuvel told to TOI in an exclusive interaction.
Isro late on Saturday said: “The rover completed its assignments. It is now safely parked and set into Sleep mode. APXS and LIBS payloads are turned off. Data from these payloads is transmitted to the Earth via the Lander.”
“This means the command to put the rover to sleep has been enabled and it will go to sleep only Sunday as there are some tests that need to be done,” Veeramuthuvel explained.
Currently, the battery is fully charged and the solar panel is oriented to receive the light at the next sunrise expected on September 22, 2023. The receiver is kept on.
“Hoping for a successful awakening for another set of assignments! Else, it will forever stay there as India’s lunar ambassador,” Isro added.
On why an early sleep mode given that the designed life of the lander and rover were 14 Earth days, he said: “We cannot count the first two and last two days. The lunar day began on August 22 and our landing was almost at the end of the second day. From there, both Vikram and Pragyan have performed exceptionally to exceed our expectations. All mission objectives have been met and we will enter sleep mode tomorrow (Sunday).”
Why last 2 days don’t count
Elaborating on why there cannot be operations on the last two days, Veeramuthuvel said there was a need for a specific angle of the Sun’s elevation to keep systems running.
“A full lunar day is from 0° Sun elevation angle to 0° angle. But the mission is not designed like that. For landing, the angle requirement was 6-9° elevation and we managed to land when elevation was 8.75°. For operations, we need a minimum of 6° elevation angle because our cameras and other systems are characterised for that. It’s also for solar panels to remain optimal. Once it goes below 6° elevation, there’s a long shadow,” he said.
While there is a grace period for operations to continue, Isro is opting to begin the process of enabling sleep mode earlier than that. “We want to enable the sleep sequence before this grace period to avoid any last-minute challenges or hurdles. We want the lander and rover to enter the sleep mode as flawlessly as they’ve done everything else so far,” Veeramuthuvel said.
Pragyan covers 100m
In its short life on Moon, Pragyan has completed traversing more than 100 metres as of Saturday, which marked only the 10th day of its deployment, which happened early on August 24, several hours after Vikram’s soft-landing on August 23.
While 14,400 minutes make up 10 days, Pragyan, with a velocity of just 1cm/second and a host of obstacles to overcome, has moved for 167 minutes in all these days. That’s because given its size and design, its movement is highly restricted and needs meticulous planning. It can only move around 5 metres in each mobility plan executed by Isro.
Pragyan’s operations are not fully autonomous and require commands to be sent from Earth. In any given mobility plan Pragyan could have only covered 5-metres given the turnaround time. It has also had to overcome obstacles — it safely negotiated a small crater whose depth was 10cm and avoided a bigger crater with a 4-metre diametre — which would have consumed a lot of time.
“If we look specifically at the rover, we’ve managed to cover more than 100 metres in just 10 days, while several other missions that have lasted longer, even as long as six months, have only managed 100-120 metres,” Veeramuthuvel said.
Science from Moon
Between August 23 and Saturday, both Pragyan and Vikram have sent a repository of science data, some of which has been made public by Isro.
Pragyan’s Laser-Induced Breakdown Spectroscope (LIBS) and Alpha Particle X-ray Spectroscope (APXS) have confirmed the presence of sulphur, while Vikram’s Chandra’s Surface Thermophysical Experiment (ChaSTE) has measured the temperature profile of the lunar topsoil around the pole.
Another Vikram payload, the Instrument for the Lunar Seismic Activity (ILSA) recorded a “natural event” that occurred on August 26. Isro is yet to confirm the source of the event. Vikram’s RAMBHA payload has also sent data.

Source link


Please enter your comment!
Please enter your name here