Satellites no longer usable after deviation: ISRO on maiden SSLV mission

'Failure of a logic to identify a sensor failure and go for a salvage action caused the deviation,' says the Indian space agency

The Indian Space Research Organisation (Isro) on Sunday said the satellites on board its maiden Small Satellite Launch Vehicle “are no longer usable” after the SSLV-D1 placed them on an elliptical orbit instead of a circular one.

The space agency said a committee would analyse and make recommendations into today's episode and with the implementation of those recommendations “Isro will come back soon with SSLV-D2”. “SSLV-D1 placed the satellites into 356 km x 76 km elliptical orbit instead of 356 km circular orbit. Satellites are no longer usable. Issue is reasonably identified. Failure of a logic to identify a sensor failure and go for a salvage action caused the deviation,” Isro said in an update on its official Twitter handle.

It added a detailed statement by ISRO Chairman S Somanath will be “uploaded soon”. In its maiden SSLV mission, the launch vehicle carried The Earth Observation Satellite EOS-02 and the co-passenger student satellites AzaadiSAT.

SSLV had suffered ‘data loss’ in its terminal stage, after performing "as expected" in all stages. It had earlier after lifted off from the spaceport on Sunday morning. 

Unlike Isro’s trusted workhorse — Polar Satellite Launch Vehicles (PSLV) — the SSLV can carry payloads weighing up to 500 kg and deploy satellites into a 500 km low earth orbit.

It uses solid fuel — hydroxyl terminated polubutadiene —to fire the first three stages which takes the payloads to the desired altitude. 

The fourth stage comprises liquid propulsion-based Velocity Trimming Module (VTM) to place the satellites into orbit.

The objective of the EOS-02 was to provide inputs on thermal anomalies towards supporting applications in the domains of geo-environmental studies, forestry, hydrology, agriculture, soil, and coastal studies.

The AzaadiSAT carries 75 different payloads each weighing around 50 grams. Girl students from rural regions across the country were provided guidance to build these payloads which are integrated by the student team of ‘Space Kidz India’, ISRO said.

Sunday's mission of ISRO is the third this year after the successful PSLV-C53 mission on June 30, which is the dedicated commercial mission of NewSpace India.

“No longer usable”

What is SSLV?

Small Satellite Launch Vehicle (SSLV) is a 34-metre tall, about 10-metre less than PSLV, and it has a vehicle diameter of two metres as compared to 2.8 metres of PSLV

Objectives of SSLV

To provide inputs on thermal anomalies towards supporting applications in the domains of geo-environmental studies, forestry, hydrology, agri, soil & coastal studies

What was its goal?

To place satellites EOS-02 and AzaadiSAT into low earth orbit

What went wrong?

SSLV-D1 placed the satellites into 356 km x 76 km elliptical orbit, instead of 

356 km circular orbit. Isro cited the failure of the mission to ‘failure of a logic to identify a sensor failure and go for a salvage action caused the deviation’