Glitch-hit NVS-02 can provide services only for 2-3 hours per day

BENGALURU: Even as the failure analysis committee (FAC) set up to look into the May 18 PSLV failure prepares for its first formal meeting, details about the defective valve that affected India’s NV-02 navigation satellite, launched on Jan 29, have emerged, confirming that the satellite is only partially operational.In an official response to queries under right to information, Isro has conceded that NVS-02’s current orbital parameters — approximately 190km perigee (closest point to Earth) and 37,000km apogee (farthest point to Earth) — allow for only a few hours of usable Positioning, Navigation and Timing (PNT) service daily. “At present, with the given orbital parameters of NVS-02, it is estimated to provide PNT service for an average duration of 2 to 3 hours per day. But this calls for user receiver modifications and firmware updates. Technical feasibility of the same is being worked out,” Isro’s response reads.Isro’s GSLV-F15 that lifted off with the NVS-02 at 6.23am on Jan 29 had placed the satellite which is part of India’s NavIC constellation, in a geosynchronous transfer orbit (GTO) around 19 minutes later. Just a few hours later, Isro had detected a glitch in the valve that was to supply oxidiser to the liquid apogee motor (LAM). No exact reasonWithout oxidiser, Isro was unable to fire LAM, perform orbit corrections and take the satellite to the intended final orbit.The exact reason for the failure could not be ascertained, the response reads, noting that no single point failure was responsible. Test results confirmed that the issue was not related to power disconnection. Despite the reduced service window, Isro maintains that the accuracy of the PNT signal from NVS-02 will be “usable”. The NVS-02, part of India’s NavIC constellation, carries one indigenous Rubdium Frequency Standard (RAFS) and three foreign RAFS, which serve as timing sources critical to navigation accuracy. While Isro maintains that the Indian-made RAFS unit is performing comparably to their foreign counterparts, it declined to disclose technical information about the same, citing national scientific interest.PSLV failureMeanwhile, the FAC setup to investigate the cause of failure of the PSLV whose third stage (PS3) failed on May 18, was scheduled to meet for the first time on May 21. Isro chairman V Narayanan told TOI: “I have conducted the six meetings so far, including four on the day of the launch. We have to enable the FAC to conduct its meeting.”While Isro has officially said that there was a drop in chamber pressure of the third stage (PS3) motor case, it is yet to conclude on what may have caused the pressure to dip. Sources had indicated to TOI, as reported in its May 19 edition, that reasons that may have caused the drop in pressure could be: depletion of internal insulation, which affects the fuel burn, or a defective nozzle. Narayanan, however, said: “I don’t want to preempt anything at this moment and all I can say is that it is connected to the third stage.” He said that the FAC headed by M Annamalai will investigate the matter. Annamalai is a former Isro scientist who has served as director, Satish Dhawan Space Centre (SDSC) and has earlier been part of multiple FACs.