Re: [time-nuts] Space mission comes to an end because of a "computer time tagging" problem

2013-09-21 Thread Hal Murray
jim...@earthlink.net said: > Then on the ground, we time tag (with an atomic clock) when the telemetry > frame is received. (giving you "Earth Received Time" or ERT) Someone on the > ground does a process of time correlation figuring out what spacecraft time > corresponds to what TAI time, allow

Re: [time-nuts] Space mission comes to an end because of a "computer time tagging" problem

2013-09-21 Thread Jim Lux
On 9/21/13 5:41 AM, Bob Camp wrote: Hi I'd be a bit surprised if they were running anything as power hungry as an Rb all the time when a quartz based device would be smaller / lower power / lower volume. Of course they may have had mission requirements that drive them to a hydrogen maser ...

Re: [time-nuts] Space mission comes to an end because of a "computer time tagging" problem

2013-09-21 Thread Magnus Danielson
Jim, On 09/21/2013 01:32 PM, Jim Lux wrote: > On 9/21/13 2:30 AM, Rob Kimberley wrote: >> David, >> >> The satellite has probably got a Rb as its clock (hopefully more than >> one). > > Very, very few deep space probes carry a Rb ( I can't think of any off > hand). Regular old quartz, usually som

Re: [time-nuts] Space mission comes to an end because of a "computer time tagging" problem

2013-09-21 Thread Bob Camp
Hi I'd be a bit surprised if they were running anything as power hungry as an Rb all the time when a quartz based device would be smaller / lower power / lower volume. Of course they may have had mission requirements that drive them to a hydrogen maser ... Bob On Sep 21, 2013, at 5:30 AM, Rob

Re: [time-nuts] Space mission comes to an end because of a "computer time tagging" problem

2013-09-21 Thread Jim Lux
On 9/21/13 2:30 AM, Rob Kimberley wrote: David, The satellite has probably got a Rb as its clock (hopefully more than one). Very, very few deep space probes carry a Rb ( I can't think of any off hand). Regular old quartz, usually some sort of tcxo. If they are doing radio science, then it

Re: [time-nuts] Space mission comes to an end because of a " computer time tagging" problem

2013-09-21 Thread Geoff
If I was to make an educated guess about this one I'd say that it is more likely to be an overflow problem. The spacecraft was operating for significantly longer than it's builders or programmers ever considered likely. -Geoff. On Sat, 21 Sep 2013 07:30:54 pm Rob Kimberley wrote: > David, > >

Re: [time-nuts] Space mission comes to an end because of a "computer time tagging" problem

2013-09-21 Thread Rob Kimberley
David, The satellite has probably got a Rb as its clock (hopefully more than one). All I can imagine is that there has been a major clock failure of some sort, and everything is in free run and unable to sync up with ground. Thoughts? Rob -Original Message- From: time-nuts-boun...@febo.