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Chandrayaan-2: ISRO feels tilted Vikram may have compromised experiments on lunar soil


Vikram_landing_ISRO_1.JPG

BENGALURU: With 11 days to go for the desperate Indian Space Research Organisation (ISRO) scientists to re-establish contact with lander Vikram, lying tilted on the surface near the lunar south pole, scientists have said it is a “no-go” situation even if they were successful in re-linking with it.

They have said it is best to now focus on the orbiter which continues to orbit the moon with its eight payloads intact and functioning normally.

ISRO scientists, requesting anonymity, told The New Indian Express that the condition in which Vikram is lying “tilted” on the lunar surface with robotic rover Pragyan inside it, makes it extremely difficult for both to conduct the on-site experiments that were planned.

“And in the absence of the communication link, even if any of the experiments were indeed conducted by either or both of them, no data would be relayed back to earth,” one of the scientists said.

Original plans involved rover Pragyan rolling out of lander Vikram some time between 5.30 am and 6.30 am on Saturday after the latter made a soft-landing earlier at 1.53 am. But that never happened.

Just two minutes before the scheduled time of soft-landing, ISRO Telemetry, Tracking & Command Network (ISTRAC) lost communication link with the lander which was just 2.1 Km from the landing site.

ISRO chairman K Sivan said after orbiter’s camera located and clicked a snap of the lander on the lunar surface on Sunday, that it looked like Vikram had made a hard landing.

With no signals from the “tilted” lander, another ISRO scientist said it is “highly unlikely that any of the planned experiments would be able to be carried out by the lander or the rover; besides the rover itself would be unable to emerge from the lander as it can happen only after a ramp is deployed for it to roll out.

If it is tilted, it would not be possible for Pragyan to roll out as the ramp cannot be deployed. And if it did not roll out, it cannot perform any of the experiments that its two payloads are programmed to carry out.”

Between Vikram and Pragyan, there are a total of five payloads -- three on Vikram and two on Pragyan.

Besides the experiments, “The rover can communicate only with the lander, not directly with earth stations or even with the orbiter. Lander Vikram can communicate with both the orbiter and the earth stations. That is why we are desperately trying to establish contact with the lander,” said a scientist, requesting anonymity, but adding: “We should now focus on the orbiter.”

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Explaining why the on-site experiments can be compromised, he cited the example of one of the lander’s payload, Chandra's Surface Thermo-physical Experiment (ChaSTE), which measures vertical temperature gradient and thermal conductivity of lunar surface.

“It consists of sensors and a heater, which need to be inserted into the lunar regolith (layer of loose deposits covering solid rock) down to a depth of about 10 cm. How can that happen when the lander is tilted or even worse. Can such an experiment be carried out? Even if it did, what kind of data will we get when there is no communication link?” one of the scientists said, adding that the on-site segment of lunar experiments of Chandrayaan-2 are completely compromised, and that “It is now better we focus on the orbiter and its much promising payloads which are all intact. The orbiter promises to serve us over the next seven years instead of the initially planned one year.”

COMPROMISED PAYLOADS OF VIKRAM, PRAGYAN:

VIKRAM PAYLOADS

*RADIO ANATOMY OF MOON BOUND HYPERSENSITIVE IONOSPHERE & ATMOSPHERE (RAMBHA):

The lunar ionosphere is a highly dynamic plasma environment. Langmuir probes, such as RAMBHA, have proven to be an effective diagnostic tool to gain information in such conditions. Its primary objective is to measure factors such as: Ambient electron density/temperature near the lunar surface; and temporal evolution of lunar plasma density for the first time near the surface under varying solar conditions.

CHANDRA'S SURFACE THERMO-PHYSICAL EXPERIMENT (CHASTE):

ChaSTE measures the vertical temperature gradient and thermal conductivity of the lunar surface. It consists of a thermal probe (sensors and a heater) that is inserted into the lunar regolith down to a depth of abut 10 cm.

INSTRUMENT FOR LUNAR SEISMIC ACTIVITY (ILSA):

ILSA is a triple axis, MEMS-based seismometer that can detect minute ground displacement, velocity, or acceleration caused by lunar quakes. Its objective is to characterise the seismicity around the landing site.

PRAGYAN PAYLOAD:

ALPHA PARTICLE X-RAY SPECTROMETER (APXS):

APXS' primary objective is to determine the elemental composition of the Moon's surface near the landing site and detect major rock-forming elements like Sodium, Magnesium, Aluminium, Silica, Calcium, Titanium, Iron, and some trace elements such as Strontium, Yttrium and Zirconium.

LASER-INDUCED BREAKDOWN SPECTROSCOPE (LIBS):

LIBS' prime objective is to identify and determine the abundance of elements near the landing site. It does this by firing high-powered laser pulses at various locations and analysing the radiation emitted by the decaying plasma.

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