At 7 pm on Aug 31, ISRO will launch the IRNSS 1 H, a satellite that will augment India’s indigenous GPS system called NavIC (Navigation with Indian Constellation), from the Satish Dhawan Space Centre at Sriharikota.
There are seven satellites in the NavIC system currently, all launched between 2013 and 2016. The IRNSS 1 H launch was necessitated by a malfunction in the IRNSS 1A, the first satellite to be launched in this series. By mid-2016 problems surfaced with the atomic clocks onboard the satellite that helps keep time with a high degree of accuracy. It is an essential part of a navigational system.
Each satellite in the IRNSS series has three atomic clocks, one primary and two back ups. All 21 clocks that are currently onboard these satellites are manufactured by Spectracom, which is part of the Orolia Group, a conglomerate headquartered in the United States.
The atomic clocks onboard the IRNSS 1H are also from Spectracom, supplied by their manufacturing plant in Switzerland. These are rubidium-based atomic clocks, that have a high degree of accuracy unlike the electronic clocks used by earth-dwelling folk. These clocks do not lose or gain even a single second over millions of years.
“We identified the problem and the new clocks have the necessary corrections, they are purely technical in nature,” Deviprasad Karnik, spokesperson for ISRO, said but declined to shed light on the nature of the problem or the corrections.
An official at Spectrocom who spoke on the condition of anonymity said that no design changes had been made to the clocks as per his knowledge. He explained that atomic clocks like the one onboard the IRNSS could fail for many reasons including lack of improper voltage being supplied to the clock.
The IRNSS 1H will not exactly displace the IRNSS 1 A which has been relaying fuzzy data since the clock failures but rather be used in tandem.
The Rubidium atomic clocks form part of the navigation payload and the IRNSS 1H will be used for navigation services while the IRNSS-1A will continue to be used for messaging services.
The main applications of NavIC are in:
Shipping: Merchant ships use them for navigation and also for disaster management on the high seas.
Road Transport: It is used for navigation on roads as well as helping operators track their consignments and for traffic management by government agencies.
Railways: NavIC is also used to track train movements and for estimating time of arrival and departure.
Resource Management: These satellites inform the geo-tagging and geo-fencing of objects that help entrepreneurs and governments track if there is movement of goods beyond designated boundaries.
Location Based Services: Navigational satellites are essential to operations like finding nearby restaurants, shops, hospitals and petrol pumps.
Time Synchronised Services: NavIc is also used in telecom operations, power grid operations, disaster management and atmospheric studies.
PSLV launch of navigation satellite fails
Updated 6:45 p.m. Eastern.
LOS ANGELES — An Indian Polar Satellite Launch Vehicle (PSLV) failed to place a navigation satellite into its planned orbit Aug. 31 when the rocket’s payload fairing failed to deploy.
The PSLV, flying a mission designated PSLV-C39, lifted off on schedule at 9:30 a.m. Eastern from the Satish Dhawan Space Centre on the east coast of India. Initial phases of the launch appeared to go as planned, but observers noted that, as the flight progressed, the vehicle appeared to deviate from its planned trajectory according to telemetry displays shown during the webcast.
Launch controllers later confirmed that vehicle’s upper stage and payload, the Indian Regional Navigation Satellite System (IRNSS) 1H satellite, had reached a lower orbit than planned. The payload was in an orbit of 167 by 6,555 kilometers, while the planned transfer orbit for the mission was 284 by 20,650 kilometers.
A launch controller later confirmed that the rocket’s payload fairing, scheduled to separate 3 minutes and 23 seconds after liftoff during the operation of the rocket’s upper stage, had failed to do so. The additional mass of the payload fairing may account for the apparent underperformance of the PSLV’s upper stages, and would also prevent the satellite’s deployment regardless of orbit.
The Indian space agency ISRO did not immediately comment on the failure. An ISRO webcast of the launch abruptly ended shortly after the announcement of the failed payload fairing separation.
ISRO, in a statement later Aug. 31, confirmed that the payload fairing, which it calls the “heat shield,” failed to separate, dooming the mission. “[A]ll the flight events took place exactly as planned, except heat shield separation,” the agency said. “This resulted in satellite separation occurring within the heat shield. The satellite is inside the heat shield resulting in the unsuccessful mission.”
The failure is the first for the PSLV in 20 years. In September 1997, a PSLV launch placed the IRS-1D remote sensing satellite into a lower-than-planned orbit when the rocket’s fourth stage underperformed. The satellite was able to use its onboard propulsion to raise its orbit. The only total PSLV failure was rocket’s inaugural flight in September 1993, when it suffered an attitude control failure.
The failure would be a significant setback for India’s space program. The PSLV had become the workhorse for the program, launching a series of communications, remote sensing, navigation and science satellites. India had been working to increase the vehicle’s launch rate. The PSLV flew six times in 2016, and this was the third PSLV mission of 2017.
PSLV had also become a popular choice for small satellite developers, who took advantage of frequent launches to sun-synchronous orbits and excess capacity on those missions to fly as secondary payloads. A PSLV launch in February set a record for the most satellites on a single flight, with 104 payloads; all but three were cubesats provided by international customers.
The sole payload of this launch, IRNSS-1H, was intended to be a replacement for India’s first navigation satellite, IRNSS-1A, whose three onboard atomic clocks had failed. The overall IRNSS system provides position, navigation and timing data for India and the surrounding region.
Indian PSLV launch with IRNSS replacement satellite suffers apparent failure
ISRO launched a PSLV Thursday carrying a replacement satellite for the Indian Regional Navigation Satellite System (IRNSS) constellation. The IRNSS-1H satellite launched on schedule from the Second Launch Pad (SLP) at the Satish Dhawan Space Centre at 19:00 local time (13:30 UTC). However, the launch profile was off-nominal and the fairing failed to separate leading to an apparent failure of the mission.
The IRNSS-1H spacecraft was to be the eighth to be launched as part of India’s Indian Regional Navigation Satellite System (IRNSS), or NavIC, program. One of two ground spares built for the seven-satellite constellation, IRNSS-1H is being pressed into service after the failure of all three atomic clocks aboard the first IRNSS satellite, IRNSS-1A.
The second ground spare, IRNSS-1I, is also expected to launch later this year. Two further ground spares are under construction. IRNSS satellites are built and operated by the Indian Space Research Organisation, ISRO.
IRNSS uses a constellation of seven spacecraft in geosynchronous orbit to provide a navigation service covering most of Asia, the Middle East, east Africa and parts of western Australia. The program gives India a dedicated navigation system, serving military and civilian applications, reducing the country’s reliance on systems controlled by foreign governments.
Satellite navigation relies on precision timing provided by several highly-accurate atomic clocks aboard each spacecraft – three rubidium clocks in the case of an IRNSS satellite. The time of transmission is encoded in signals broadcast by a satellite, which receivers can use to work out the time taken for the signals to reach it – and hence the receiver’s distance from the spacecraft.
By triangulating the distance of the receiver from four satellites, whose precise locations in space are known through orbital ephemeris broadcast along with the timing data, a location can be computed in three dimensions.
The problems aboard IRNSS-1A began in mid-2016 with the failure of one of its three atomic clocks. The remaining two failed over the following six months.
Without the clocks in operation the satellite cannot produce a sufficiently accurate signal to be used for precise navigation, although it is continuing to broadcast system messages. At launch in July 2013, the spacecraft was expected to provide ten years of service.
The clocks aboard IRNSS satellites were built by Swiss company SpectraTime. Several satellites in the European Galileo navigation constellation, which also uses rubidium atomic clocks built by the same contractor, have experienced similar failures. IRNSS-1H will use modified versions of the same clocks as its predecessors.
IRNSS-1H is a 1,425-kilogram (3142 lb) satellite which is expected to provide ten years of service. It will be stationed in an inclined geosynchronous orbit at longitude of 55 degrees East, where it will replace IRNSS-1A.
The satellite is of the same design as its predecessor, based around ISRO’s I-1K bus, with the same ten-year design life.
Four of the seven satellites in the IRNSS constellation are deployed in inclined orbits, with two each at 55 and 111.75 degrees East. The remaining three satellites are in equatorial geostationary orbits, at 34, 83 and 129.5 degrees East.
Deployment of IRNSS began in July 2013, with the launch of IRNSS-1A, while the April 2016 launch of IRNSS-1G completed the initial constellation. All seven satellites in orbit were launched by ISRO using PSLV-XL vehicles, the same type of rocket that was tasked with delivering IRNSS-1H to orbit on Thursday.
The Polar Satellite Launch Vehicle, or PSLV, is the workhorse of India’s space program. First flown in September 1993, it has completed thirty-eight successful missions from forty launches prior to Thursday. The rocket’s last thirty-six consecutive launches, spanning almost twenty years, have been successful. This apparent failure would be a rare loss for ISRO in its recent successful era.
PSLV is a four-stage rocket, using a combination of solid and liquid-fuelled stages. In its standard configuration, the PSLV-G, the rocket is augmented at liftoff by six strap-on solid rocket motors, although the lower-capacity PSLV-CA version omits these. The PSLV-XL configuration, first flown in 2008, uses six more powerful strap-ons to achieve a higher payload capacity.
Thursday’s launch used PSLV C39, a PSLV-XL vehicle which will fly from the Second Launch Pad (SLP) at the Satish Dhawan Space Centre on Sriharikota Island. The Satish Dhawan Space Centre, previously named the Sriharikota High Altitude Range (SHAR), has been the point of departure for all of India’s orbital launches.
The Second Launch Pad was built in the early 2000s to support launches of ISRO’s PSLV rocket, as well as the larger Geosynchronous Satellite Launch Vehicle (GSLV), alongside the nearby First Launch Pad (FLP). Unlike the First Launch Pad, where rockets are assembled at the pad, rockets launched from the Second pad are integrated atop a mobile platform in the complex’s Vehicle Assembly Building.
PSLV C39’s launch began with ignition of the first stage once Thursday’s countdown reached zero. The first stage, or PS1, uses an S-138 solid rocket motor. The first four PS0M-XL strap-on boosters ignited 0.42 and 0.62 seconds later, as the PSLV began its ascent. The final pair of boosters are air-lit, beginning their burn 25 seconds after liftoff.
Each booster consists of an S-12 solid rocket motor. After burnout, the two pairs of ground-lit boosters separated from the rocket at 69.9 seconds and 70.1 seconds mission elapsed time, while the air-lit boosters separated 92 seconds into the flight.
Burnout and separation of the PSLV’s first stage occurred one minute and 50.26 seconds after liftoff, with the second stage igniting its Vikas engine two tenths of a second later. The second stage, designated PS2 or L-40, is liquid-fuelled and burns UH25 propellant oxidized by dinitrogen tetroxide.
The Vikas engine is a license-built derivative of the French Viking engine, which powered the Ariane 1, 2, 3 and 4 rockets. It burned for about two-and-a-half minutes. The payload fairing – or “heat shield” in ISRO parlance – was to separate from the nose of the rocket 92.8 seconds into the second stage burn – however, this never occurred, pointing to the first issue for the launch.
Four minutes and 23.08 seconds after liftoff, the second stage separated from the vehicle. The PS3 third stage ignited its solid-fuelled S-7 motor 1.2 seconds later, for a burn of about seventy seconds. A coast phase followed third stage burnout. At this point the overlaps on the mission control center showed misalignment, pointing to an issue.
At ten minutes, 6.72 seconds mission elapsed time, the spent third stage was jettisoned. Ten seconds later, fourth stage ignition took place. The PS4, or L-2.5, fourth stage is liquid-fuelled burning monomethylhydrazine (MMH) and mixed oxides of nitrogen (MON). It burned for eight minutes and 31.66 seconds.
Thirty-seven seconds after the fourth stage completed its burn, IRNSS-1H appeared to have separated, as images showed the satellite moving around inside what was an unintentional fairing prison.
The satellite was aiming to be separated into a subsynchronous transfer orbit, with a perigee of 284 kilometers (177 miles, 153 nautical miles), an apogee of 20,650 km (12,831 mi, 11,150 nmi) and 19.2 degrees inclination.
The margin of error for the launch is five kilometers (3.1 miles, 2.7 nautical miles) for the perigee, 675 km (419 mi, 365 nmi) for the apogee and 0.2 degrees for the inclination. IRNSS-1H was to use its onboard propulsion system to maneuver to its final geosynchronous orbit.
Thursday’s launch was the fifth of 2017 for ISRO, and the third of the year for the PSLV, following June’s successful deployment of CartoSat-2E aboard another PSLV-XL. ISRO’s next launch is expected to occur in November, with PSLV-XL C40 delivering IRNSS-1I into orbit. However, the impact on this failure on the schedule is currently unknown.
Top space scientists back ISRO to bring PSLV back to its glory
As the heatshield failed to separate from the satellite, ISRO's 8th navigation satellite launch IRNSS-1H was termed as unsuccessful and scientists have undertaken an analysis to study the cause of the incident. PTI Photo
Striking a note of caution against complacency, they urged team ISRO not to lose heart and reposed confidence in the space agency's ability to bounce back.
The PSLV-C39 mission carrying the replacement navigation satellite IRNSS-1H failed yesterday. ISRO said PSLV-C39 had a normal lift-off and all the flight events took place exactly as planned, except heat shield separation.
"This resulted in satellite separation occurring within the heat shield. The satellite is inside the heat shield resulting in the unsuccessful mission. Detailed analysis is in progress to identify the cause of the anomaly in the heat shield separation event", according to ISRO.
Former ISRO Chairman K Kasturirangan said the space agency has gone through unsuccessful missions in the past, particularly in the early phase of the country's space programme.
"Every time we have come back with redoubled vigour and made sure that not only it (failure) does not repeat, the probability of these things happening is minimised," he told PTI.
"But space is certainly a risky endeavour. So, one has to keep an allowance for it. One should not be complacent, do the best and then leave the rest of it to providence because there is a small component of probability that in spite of every thing being done, in what we call as perfect, there can something which can be residual. So, we should not be complacent," Kasturirangan said.
"We had an extraordinary string of successes with PSLV, so it's all the more hurting because of the fact that we expect 100 per cent success every time to we do with PSLV," he said.
Kasturirangan said he has no doubt ISRO would move forward with redoubled vigour and greater determination.
"One satellite was involved and certainly (it's) a setback in that sense but there is no question of looking back; we have to look forward; they (ISRO) have got a big agenda for space and ambitious agenda; it can be fulfilled only with courage of conviction, determination and exceptional technical professionalism. In all these, ISRO is now well known and established its credentials," he said.
Former ISRO Chairman, G Madhavan Nair described the unsuccessful mission as "very unfortunate".
"PSLV had a good track record. About 40 launches it has done. Now, a failure like this is difficult to digest," he said.
But Nair noted: "Failures are not uncommon. If you look at the global scenario, five to ten per cent is a failure rate of proven launch vehicles itself. Compared to that, we were hardly one failure in 40. That's our record. It has become two (failures out of 40 launches). We cannot be satisfied with statistics. We have to be concerned about it."
"I am sure ISRO team will be able to find why and how it (the failure) has happened, and fix it, and come back to launch pad as quickly as possible. That's been ISRO culture. My message to ISRO team, they should not lose heart, go hard into failure reason and fix it," he told PTI.
Another former ISRO Chairman K Radhakrishnan tweeted: "Team@ ISRO, Don't get disheartened with the outcome of PSLV-C39. Intrinsic resilience will bring PSLV back to its glory soon. Move ahead boldly".
PSLV had a record of 39 consecutive successful launches ever since its maiden flight failed more than two decades ago.
ISRO launch ‘unsuccessful’: What is heat shield and why was IRNSS-1H satellite not released?
The ISRO chairman described the mission as a “mishap” after announcing that the IRNSS-1H satellite was not released by the rocket.
India’s mission to place a navigation satellite into space failed on Thursday after the spacecraft carrying it suffered a technical fault on the final leg after a perfect launch.
Indian Space Research Agency (ISRO) chairman Kiran Kumar described the mission as a “mishap” shortly after announcing that the IRNSS-1H satellite was not released by the PSLV-39 rocket as the heat shield didn’t separate from the spacecraft.
Thursday’s setback is considered a rare failure in India’s space mission involving the PSLV, dubbed as ISRO’s ‘workhorse’, which has had a time-tested record of 39 consecutive successful launches. Before this, its maiden flight failed 24 years ago.
What is a heat shield?
A heat shield is an encasement which protects the satellite in the rocket from ultra-high temperatures, acoustic pressures that the spacecraft experiences while travelling in the Earth’s atmosphere, an article in the Indian Express said.
In space shuttles, the heat shield must protect the crew capsule and its precious astronaut crew from temperatures that can melt metal. These ultra-high temperatures result from friction between the air and the speeding spacecraft, according to Nasa.
Heat shield separation and satellite
Pressures decrease once the spacecraft is outside Earth’s atmosphere, allowing the heat shield to separate in the fourth phase of the launch.
After the heat shield failed to separate, the IRNSS-1H satellite could not be released into the orbit.
The eighth satellite was a replacement for IRNSS-1A, one of the seven satellites in India’s navigation satellite constellation, as its three rubidium atomic clocks on board had stopped functioning. It was also the first time the private sector was actively involved in assembling and testing of a satellite.
ISRO said it will probe why the shield didn’t peel off.