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#40 by vyoma on 07 Sep, 2016 17:20
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As per report in this post, it'll be a spare satellite kept on ground.
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#41 by vineethgk on 05 Oct, 2016 05:42
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IAF faces longer wait for own satellite as Isro yet to get nodQuote
Singh said the decisions were being taken at the Air Force headquarters and by Isro. He, however, confirmed that the IAF will soon be migrating to the indigenised version of GPS, using Isro's Indian Regional Navigation Satellite System (IRNSS).
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#42 by vineethgk on 06 Oct, 2016 14:42
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PEC to collaborate with SAC for ISRO projectQuote
Chandigarh: PEC University of Technology will working with institutions to collect data for the Indian Regional Navigation Satellite System (IRNSS) programme of ISRO, named as NAVIC (acronym for NAVigation using Indian Constellation)
QuoteThe college will receive four receivers soon which will be used in research and teaching methods. Besides this, the college will work on small projects and the performance of these will be examined for a year.
QuotePEC has signed a memorandum of understanding with SAC, which has additionally roped in various other technical institutes from the country for the IRNSS data collection exercise using SAC-developed IRNSS ground receiver.
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#43 by vyoma on 18 Jan, 2017 17:54
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Galileo satellites experiencing multiple clock failuresQuote
The onboard atomic clocks that drive the satellite-navigation signals on Europe's Galileo network have been failing at an alarming rate.
Across the 18 satellites now in orbit, nine clocks have stopped operating.
Three are traditional rubidium devices; six are the more precise hydrogen maser instruments that were designed to give Galileo superior performance to the American GPS network.QuoteEsa is also in contact with the Indian space agency which is using the same clocks in its sat-nav system. So far, the Indians have not experienced the same failures.
QuoteMost of the maser failures (5) have occurred on the satellites that were originally sent into orbit to validate the system, whereas all three rubidium stoppages are on the spacecraft that were subsequently launched to fill out the network.
QuoteIt appears the rubidium failures "all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground".
QuoteThe maser clock failures are said to be better understood, with two likely causes, the second of which has caused most grief.
The Esa statement said this second scenario was "related to the fact that when some healthy [hydrogen maser] clocks are turned off for long periods, they do not restart due to a change in clock characteristics". -
#44 by vyoma on 18 Jan, 2017 18:01
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IRNSS satellites are using similar Rubidium atomic clocks sourced from same manufacturer/vendor (Spectratime) as that of ESA.
Hope those failures seen on Galileo are one off cases
ISRO should switch to indigenous clocks ASAP.
Rubidium clock failures are seen in operational Galileo satellites. First operational Galileo was launched in 2011, and first operational IRNSS was launched in 2013. So, there's not much difference in terms of aging of clocks.
ESA is suspecting some kind of short circuit in Rubidium clocks, linked to a certain test procedure done on ground. -
#45 by chota on 25 Jan, 2017 11:28
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Galileo satellites experiencing multiple clock failures
QuoteThe onboard atomic clocks that drive the satellite-navigation signals on Europe's Galileo network have been failing at an alarming rate.
Across the 18 satellites now in orbit, nine clocks have stopped operating.
Three are traditional rubidium devices; six are the more precise hydrogen maser instruments that were designed to give Galileo superior performance to the American GPS network.QuoteEsa is also in contact with the Indian space agency which is using the same clocks in its sat-nav system. So far, the Indians have not experienced the same failures.
QuoteMost of the maser failures (5) have occurred on the satellites that were originally sent into orbit to validate the system, whereas all three rubidium stoppages are on the spacecraft that were subsequently launched to fill out the network.
QuoteIt appears the rubidium failures "all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground".
QuoteThe maser clock failures are said to be better understood, with two likely causes, the second of which has caused most grief.
The Esa statement said this second scenario was "related to the fact that when some healthy [hydrogen maser] clocks are turned off for long periods, they do not restart due to a change in clock characteristics".
There you go !!. One of the IRNSS satellite has developed a problem !!.
It seems India is using Spectratime-built atomic clocks as is the case with China
http://www.ndtv.com/india-news/indias-swadeshi-gps-develops-a-problem-but-remains-functional-1652638
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#46 by vineethgk on 25 Jan, 2017 14:02
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Oops. This is turning out to be a really costly issue. A disaster of sorts if both ESA and ISRO ultimately end up replacing its entire navigation constellation. For India, this would be quite critical as both ISRO and the defense agencies were planning to utilize NavIC for their respective strategic requirements. Does this indicate the problem was likely with the clocks themselves, and not due to test procedures or associated instruments?Galileo satellites experiencing multiple clock failures
QuoteThe onboard atomic clocks that drive the satellite-navigation signals on Europe's Galileo network have been failing at an alarming rate.
Across the 18 satellites now in orbit, nine clocks have stopped operating.
Three are traditional rubidium devices; six are the more precise hydrogen maser instruments that were designed to give Galileo superior performance to the American GPS network.QuoteEsa is also in contact with the Indian space agency which is using the same clocks in its sat-nav system. So far, the Indians have not experienced the same failures.
QuoteMost of the maser failures (5) have occurred on the satellites that were originally sent into orbit to validate the system, whereas all three rubidium stoppages are on the spacecraft that were subsequently launched to fill out the network.
QuoteIt appears the rubidium failures "all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground".
QuoteThe maser clock failures are said to be better understood, with two likely causes, the second of which has caused most grief.
The Esa statement said this second scenario was "related to the fact that when some healthy [hydrogen maser] clocks are turned off for long periods, they do not restart due to a change in clock characteristics".
There you go !!. One of the IRNSS satellite has developed a problem !!.
It seems India is using Spectratime-built atomic clocks as is the case with China
http://www.ndtv.com/india-news/indias-swadeshi-gps-develops-a-problem-but-remains-functional-1652638
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#47 by eeergo on 25 Jan, 2017 14:11
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Does this indicate the problem was likely with the clocks themselves, and not due to test procedures or associated instruments?
According to this: https://www.spaceintelreport.com/galileo-clocks
"Javier Benedicto, head of the Galileo Program Department at the 22-nation ESA, said the investigation has tentatively concluded that the issues do not relate to the core technology provided by SpectraTime.
In an interview, Benedicto said that while the root cause of the failure likely is to be found inside the clocks, it is more likely to be of a peripheral piece of circuitry or other unremarkable component that, when operated in a certain way, leads to failure.
“We have 72 clocks in orbit today,” Benedicto said. “Of these, we have had up to six failures. We have not been able to replicate those failures on the ground. These units all passed their qualification and acceptance tests.”
[...]“It is not a development issue with the clocks,” Benedicto said. “It is not a fundamental part of the unit that is failing.They were not bound to fail. But in certain conditions where you have certain parameters going in the wrong direction together, it could cause the unit to fail. You have to be particularly unlucky and have all the failure parameters drifting in a specific direction."" -
#48 by sanjaykumar on 25 Jan, 2017 15:03
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http://www.ndtv.com/india-news/indias-swadeshi-gps-develops-a-problem-but-remains-functional-1652638Quote
India's Swadeshi GPS Develops A Problem, But Remains Functional
"The on-board atomic clock has developed a problem and we are trying to revive it," said Dr. Kiran Kumar, Chairman of ISRO or the Indian Space Research Organization, to NDTV. -
#49 by vineethgk on 25 Jan, 2017 15:17
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“It is not a development issue with the clocks,” Benedicto said. “It is not a fundamental part of the unit that is failing.They were not bound to fail. But in certain conditions where you have certain parameters going in the wrong direction together, it could cause the unit to fail. You have to be particularly unlucky and have all the failure parameters drifting in a specific direction.""
But if the failures in the cases of Galileo and IRNSS indeed turn out to follow a similar pattern (too early to say at the moment as ISRO is yet to publish its share of details), it may not be a case of being 'particularly unlucky' after all.
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#50 by vyoma on 26 Jan, 2017 01:23
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Not sure what they mean by "satellite's not visible"!?
Also, as per this €4M contract between SpectraTime and ISRO, each satellite has (or supposed to have), 4 Rubidium clocks. So, there should be some sort redundancy.Quote. In the framework of the IRNSS program, each satellite will have four SpectraTime Rubidium atomic clocks on board to reach a stability of less than 10 billionths of a second per day. « To give a point of comparison, our clocks are 10 million times more precise than a watch made of quartz" », says Pascal Rochat, Chief Executive Officer of SpectraTime.
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#51 by vyoma on 30 Jan, 2017 01:58
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Atomic clocks on indigenous navigation satellite develop snagQuote
In the NavIC, a constellation of seven satellites, one of the three crucial rubidium timekeepers on IRNSS-1A spacecraft failed six months ago. The other two followed subsequently.
QuoteA. S. Kiran Kumar, Chairman of the Indian Space Research Organisation, confirmed the glitch in the clocks but clarified that the satellite was otherwise all right, and the rest of the satellites were performing its core function of providing accurate position, navigation and time. However, without its clocks, the IRNSS-1A “will give a coarse value. It will not be used for computation. Messages from it will still be used.”
Quote“There are some anomalies in the atomic clock system on board. We are trying to restart it. Right now we are working out a mechanism for operating it,” he told The Hindu.
“The problem is only with the clock system of one spacecraft. The signals are all coming, we are getting the messages, everything else is working and being used, except the stability portion which is linked to the clock,” he said. A minimum of four working satellites was sufficient to realise the full use of the navigation system”.QuoteNavIC has 21 atomic clocks on seven spacecraft. “How would the other clocks fare? Would ISRO reconsider the supplier of its atomic clocks? Such questions are not easy to answer. Generally any [space] hardware is an issue. We have to find ways of going around it,” he said.
QuoteThe troubled IRNSS-1A spacecraft was put in space in July 2013 and has an expected life span of 10 years.
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#52 by vyoma on 30 Jan, 2017 02:07
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I hope ISRO, ESA and Spectratime figure out the issue, and if possible recalibrate/reconfigure atomic clock hardware on other satellites to avoid further failures.
ISRO has imported 29 Rubidium clocks from SpectraTime, 21 of them are used in IRNSS-1A to 1G. Hopefully, they'll sort out the issue before remaining two backup satellites are built.Quote2010: First RAFS rubidium clocks flying & operating on the COMPASS/Baidu satellites
2011: Prime Swiss supplier of the PHM maser & RAFS rubidium clocks for Galileo's 14 satellites
2012: Prime Swiss supplier of 29 space RAFS rubidium clocks for the IRNS (Indian Regional Navigation System)
2015: Prime Swiss supplier of all PHM maser & RAFS rubidium clocks for the first 22 Galileo satellites
Even Chinese COMPASS and DFH satellites are using Spectratime Rubidium clocks, not sure if they've hit similar snags?!
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#53 by vineethgk on 30 Jan, 2017 02:15
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I hope ISRO, ESA and Spectratime figure out the issue, and if possible recalibrate/reconfigure atomic clock hardware on other satellites to avoid further failures.
Since the snag has hit the first IRNSS satellite at the moment, I really really hope it isn't a matter of time before the rest starts to show the same anomaly in sequence.
Even Chinese COMPASS and DFH satellites are using Spectratime Rubidium clocks, not sure if they've hit similar snags?!
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#54 by vyoma on 30 Jan, 2017 03:29
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Yes
Rb clock failures are seen in two of the Galileo's operational constellation satellites (FOC). Considering first FOC was launched in 2014 and first IRNSS was launched in 2013, looks like these clocks are developing anomaly after approximately 3 years of operation (either due to inherent issue in clocks or satellite subsystem)!!
But, ESA's GIOVE-A/B and Galileo IOV (In-Orbit Validation) experimental satellites had same Rb clocks, and they didn't seem to have any failures after years of operation. Hopefully ESA, ISRO would be comparing GIOVE-A/B or IOV hardware with FOC or IRNSS hardware. -
#55 by chota on 30 Jan, 2017 05:00
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Alarming !! All three clocks have failed – one primary and two backups
Replacement satellite 1H planned
https://thewire.in/103934/atomic-clock-rubidium-irnss/
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#56 by vyoma on 30 Jan, 2017 05:43
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Alarming !! All three clocks have failed – one primary and two backups
Replacement satellite 1H planned
https://thewire.in/103934/atomic-clock-rubidium-irnss/
Would be really interesting to know how those clocks are faring in CNSA's satellites. Anyway, IRNSS-1H is going to to be built same hardware, not sure if it really helps in the long run. -
#57 by vineethgk on 30 Jan, 2017 05:55
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Chinese may not readily acknowledge such a failure even if it had occurred, which is perhaps why there aren't reports of ESA contacting them yet. For that matter, even in India's case, was it perhaps the reports of Galileo's string of failures that encouraged ISRO to go public about this now?Alarming !! All three clocks have failed – one primary and two backups
Replacement satellite 1H planned
https://thewire.in/103934/atomic-clock-rubidium-irnss/
Would be really interesting to know how those clocks are faring in CNSA's satellites. Anyway, IRNSS-1H is going to to be built same hardware, not sure if it really helps in the long run.
As for IRNSS-1H, they might be banking on it as a stop-gap replacement at best until they figure out what exactly went wrong. NavIC is a crucial piece of equipment for India's strategic needs, and ISRO may not risk any dent in its capability even for a short term.
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#58 by vyoma on 31 Jan, 2017 14:29
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http://gadgets.ndtv.com/science/news/isro-to-launch-standby-navigation-satellite-to-replace-irnss-1a-1654441Quote
India will launch one of its back up navigation satellites this year as a replacement to IRNSS-1A satellite, whose three atomic clocks have failed, an official of the Indian space agency said on Monday.
The official denied the existence of similar problems with the rubidium atomic clocks in another navigation satellite.
"The atomic clocks have failed in only one satellite. We will be launching the stand-by satellite this year. All other six satellites are operational and are providing the navigation data," A.S. Kiran Kumar, Chairman, Indian Space Research Organisation (ISRO), told IANS.
He said the atomic clocks were imported and ISRO would take up the issue with the foreign supplier.
Each satellite has three clocks and a total of 27 clocks for the navigation satellite system were supplied by the same vendor. The clocks are important to provide precise data. -
#59 by worldtimedate on 31 Jan, 2017 17:50
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Quote
Atomic clocks failures onboard Galileo satellites
SSTL_PHMAcross the 18 satellites now in orbit, nine clocks out of 72 have stopped operating. Three are traditional rubidium devices; six are the more precise hydrogen maser instruments that were designed to give Galileo superior performance to the American GPS network.
Mitigating actions
It appears the rubidium failures all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground.
The maser clock failures are said to be better understood, with two likely causes, the second of which has caused most grief. The ESA statement said this second scenario was related to the fact that when some healthy [hydrogen maser] clocks are turned off for long periods, they do not restart due to a change in clock characteristics.
Source : Atomic clocks failures onboard Galileo satellites | GALILEO:QuoteGalileo clock anomalies under investigation
As first reported last November, anomalies have been noted in the atomic clocks serving Europe’s Galileo satellites.
Anomalies have occurred on five out of 18 Galileo satellites in orbit, although all satellites continue to operate well and the provision of Galileo Initial Services has not been affected.
Source : Galileo clock anomalies under investigation | GALILEO:
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ISRO should switch to 
Rb clock failures are seen in