ISRO Chairman S Somanath weighs in on SSLV launch; 'vehicle's performance was very good'

The developmental mission for ISRO's new Small Satellite Launch Vehicle (SSLV) fell short of success as it failed to insert two satellites into the desired orbit during the SSLV-D1/EOS-02 mission. After lifting off at 9:18 am today, the SSLV rocket performed as expected, however, a data loss was observed during the terminal stage. In an official statement, ISRO later confirmed that the satellites are placed in an orbit lower than expected and that the two satellites-- AzaadiSAT and EOS-02-- are no longer usable.

The issue is said to have emerged in the velocity trimming module (VTM), SSLV's terminal stage, which was supposed to burn for 20 seconds, around 653 seconds after launch in order to raise the rocket's stage to the target altitude. The VTM, however, burned for just 0.1 seconds, resulting in the failure. 

[The satellites AzaadiSAT (left) and the EOS-02 (bigger one on the right) placed on the VTM at the Satellite preparation facility Satish Dhawan Space Center; Image: Twitter/@SpaceKidzIndia]

ISRO Chairman S Somanath weighs in on the issue

Following the confirmation, ISRO Chairman S Somanath, in a video message, addressed the issue and revealed what caused the SSLV mission anomaly. He said that the deviation from the intended orbit resulted from the failure of logic (in the rocket stage) to identify a sensor failure and go for a salvage action. 

According to the ISRO Chairman, the new-generation rocket's first solid stage and the subsequent stages (second and third) performed exactly as expected. "The entire vehicle's performance was very good and finally when it reached an altitude of 356 km, both satellites were separated", Somanath said. He further revealed that the mission teams observed that both the satellites are in an elliptical orbit instead of a circular orbit.

While an altitude of 356 km was the intended orbit, the satellites were inserted at 356X76 km, with 76 km being the lowest distance from the Earth's surface. The ISRO chief explained that when satellites are placed in such an orbit, they will not remain stable as the atmospheric drag will bring them down. He said that the AzaadiSAT and the EOS-02 have already lost altitude and they are no longer usable.

What's next for ISRO?

The ISRO Chairman also said that apart from the issue of the logic failure, the mission team did not find any other anomaly and that every element of the new rocket - the propulsion stages, the hardware, control systems, electronics - everything worked really well. "We are very happy about that", he added. "What were are going to do now is to identify the specific problem, we will conduct a detailed evaluation in the days to come," Somanath said and asserted about forming a committee to analyse the problem and implement its recommendations. 

He also confirmed that ISRO will soon be back on the launch pad with a second demonstration mission of the SSLV rocket to establish its capabilities to launch small satellites using completely indigenous technology. Weighing over 120 tonnes and standing 34 metres tall, the rocket has been developed with a total payload capacity of 500 kg to launch small and microsatellites.