Mission half accomplished

Chandrayaan-1 loses radio contact with the ground station

The Deep Space Network (DSN) at Byalalu near Bangalore received the last data at 12.25 am and stopped getting signals altogether at 1.30 am on Saturday morning.

Dr Satish, spokesperson, Indian Space Research Organisation (ISRO), said the mission was not officially over, until the last received telemetry data had been analysed.

“We have not been able to transmit any commands or receive any data since 1.30 am this morning. We are analysing the progress and health of the spacecraft subsystems and hope this will throw some light on what happened. We will analyse whether there was any gradual degradation of data that was being received. At the present juncture, however, the mission has not been terminated,” he said.

Time frame

He refused to give a time frame for the analysis of the data. Though ISRO officials maintained that the radio contact was lost on Saturday morning, sources who are working on the project, told  Deccan Herald that the data from the spacecraft had stopped coming in as early as Thursday.  “All the three ground stations, DSN at Byalalu, Jet Propulsion Labs and Applied Physics Labs in the US, stopped receiving signals on Thursday,” sources said.

Chandrayaan-1 is tracked by all the three centres throughout the day. DSN for instance, does not receive signals from the spacecraft for a maximum of 7 hours a day. During this time, the other two ground stations receive signals. But no total analysis of the data and or any crucial manoeuvring is possible at these two ground stations.

Sources at DSN termed it a serious problem and they would continue trying to establish contact as well as investigate the data for any problems on the subsystems. “We expected the mission to last for at least a year, so we are feeling bad. We never expected it to end so abruptly. But most of the data have been collected, so we are quite satisfied with the fact that we have met with most of the mission objectives,” the source commented.

The loss of radio contact is the latest in the series of failures, after the loss of Bus Management Unit (BMU) and the star sensor in July. 

According to ISRO, “the Attitude and Orbit Control subsystem, essentially the brain of Chandrayaan-1, consisting of a Bus Management Unit (BMU), reaction wheels and thrusters, ensures the proper orientation and stability of the spacecraft as well as in changing its orbit during different phases of its flight.”

BMU failure

This BMU, according to sources, stopped working in the first month of the launch. However, it was replaced with the back-up unit, thereby preventing any problem. However, officials refused to confirm the date of BMU failure.

Saturday’s development is the latest in  a series of technical failures that plagued Chandrayaan-1.  In April this year, the star sensor, used for determining the attitude and orientation, suffered a failure and was replaced with gyroscopes to do the job.
This was revealed only a couple of months later. Incidentally, the ISRO issued a statement, within 12 hours of the loss of radio contact.

When asked about ISRO’s hurry to issue a statement, Dr Satish, ISRO spokesman, said in the other cases (star sensor and BMU), they were instantly replaced with back up instruments, so there was no need to explain. “But this is a serious road block,” he maintained.

Chandrayaan-I was launched from Satish Dhawan Space Centre Sriharikota on October 22, 2008, with11 payloads. One of the payloads, the Moon Impact Probe, landed on the moon on November 14, 2008. The spacecraft which had a mission life of two years,  has completed 312 days in orbit making more than 3,400 orbits around the Moon.