[time-nuts] new gps sat prn30 svn64

Skip Withrow swithrow at alum.mit.edu
Sun Mar 2 16:06:21 EST 2014


> 
> svn64 alive and well
> 
> Using sirfdemo pc software coupled with sirf iv gps receiver I picked up 
the first signal from svn64 (now
> assigned prn30).
> The sat was launched from cape canavral (airforce station) florida last 
thursday evening 2-20-14 about 17:55pdt.
> The gps control people seem to be turning on the satellites transmitter 
intermittantly.
> The new satellite will not be in its final orbit for approximately 30 
days and not usable till about 36 days
> from its launch 
> 
> date.
> 
> My first reception was at 23:32:22pdt
> 
> gps time error		freq-drift	   date	     time pdt
> 
> 4.4716290517e-010,-1.1166002510e-014	 <at>  02/21/2014 23:32:22
> 2.7434175598e-010,-5.1373205549e-014	 <at>  02/22/2014 00:57:22
> 2.7264644019e-010,-5.1373205549e-014	 <at>  02/22/2014 00:57:52
> 2.7202887741e-010,-5.2401886405e-014	 <at>  02/22/2014 00:58:22
> 2.7003760573e-010,-5.2401886405e-014	 <at>  02/22/2014 00:58:52
> 2.6877996045e-010,-5.2401886405e-014	 <at>  02/22/2014 00:59:22
> 2.6416859445e-010,-5.2401886405e-014	 <at>  02/22/2014 01:00:52
> 2.5693992947e-010,-5.3422655975e-014	 <at>  02/22/2014 01:02:52
> 2.5624543494e-010,-5.3422655975e-014	 <at>  02/22/2014 01:03:22
> 2.5421537401e-010,-5.3422655975e-014	 <at>  02/22/2014 01:03:52
> 2.4365104104e-010,-5.4384875238e-014	 <at>  02/22/2014 01:06:52
> 2.4196987886e-010,-5.5335398671e-014	 <at>  02/22/2014 01:07:22
> 2.3208415713e-010,-5.6217685129e-014	 <at>  02/22/2014 01:10:22
> 2.3084736806e-010,-5.6217685129e-014	 <at>  02/22/2014 01:10:52
> 2.1308972996e-010,-5.7062414147e-014	 <at>  02/22/2014 01:15:52
> 2.1229085616e-010,-5.7062414147e-014	 <at>  02/22/2014 01:16:22
> 2.1024898532e-010,-5.7873397372e-014	 <at>  02/22/2014 01:16:52
> 1.7422816710e-010,-6.0095673013e-014	 <at>  02/22/2014 01:26:52
> 1.4985197051e-010,-6.1364392842e-014	 <at>  02/22/2014 01:33:52
> -8.2096225744e-011,-6.4458299267e-014	 <at>  02/22/2014 02:33:22
> -8.7252889686e-011,-6.4458299267e-014	 <at>  02/22/2014 02:34:52
> -8.8348680774e-011,-6.4458299267e-014	 <at>  02/22/2014 02:35:22
> -1.0635115866e-010,-6.3795634899e-014	 <at>  02/22/2014 02:39:52
> -1.0947714477e-010,-6.3795634899e-014	 <at>  02/22/2014 02:40:52
> -1.2733387921e-010,-6.2957112939e-014	 <at>  02/22/2014 02:45:22
> 
> This is a complete list of all that was received from the new prn30 
satellite (so far). perhaps there saving
> power till solar 
> 
> pannel deployment? or are saving power to charge batterys after just 
deploying solar pannels?
> 
> The numbers were cut an pasted from message id 30 (nl sv state data) 
from the sirfdemo pc software logging feature.
> I've been monitoring this information for the last 8 weeks logging many 
days of satellite data.
> 
> It appears that gps time error gets updated from the satellite broadcast 
navagation message at least daily.
> I believe that the gps receiver then computes the satellite frequency 
drift (including doppler shift) and
> computes gps time 
> 
> error till the next satellite navagation broadcast message updates the 
accumulated time error.
> 
> Atomic clocks in gps orbit run 45us fast perday due to less gravity but 
loose 8 us per day do to 
> there high velocity. the net result is 37us per daily. 
> 
> It looks like the new satellite clock is keeping excellant time for not 
being in orbit yet.. perhaps it is
> allready high 
> 
> enough above earth to not experience the slower time of earths gravity?
> 
> The old Prn30 has been flagged unusable for years. but data was still 
received and logged with sirfdemo. 
> 
> This is the last data from the old satellite prn30 (norad number 34661) 
whose transmissions became
> intermittant the last week 
> 
> (control operators turning it off and on).
> 
> gps time error     frequency drift
> 6.7348954278e-004,2.8731554896e-012	 <at>  02/21/2014 11:21:28 = last 
intermittant message from the old
> prn30 satellite.
> 
> My gps receiver is a bu-353s4 (sirf-4) usb dongle that is available on 
ebay for about $40 dollars. My old
> sirfIII worked a 
> 
> little better (globalsat holux gr-213u). the new sirf IV spitts unwanted 
data randomly into log file.
> random data labeled 
> 
> unk:hexadecimal strings no help on internet but many complaints.. 
sirfdemo software is still
> downloadable from the internet.
> 
> Nothing else has been received sense 02:45. I dont know if the sat is 
still visable to the usa right now or if
> the 
> 
> transmissions have been disabled .. 
> There isn't any information on the internet yet.. No norad satellite 
numbers (svn64) published for
> tracking it yet.
> 
> Enjoy. hope my tabs and spaces keep data aligned..
> 
>
 
Hello Tom,
Just wondering if we are looking at the same data?  I have been using 
SiRFDemo with a BU353S4 and looking at the Message 30 output.  Currently 
(2pm MT 2Mar2014) PRN30 clock bias is 1.3294214026e-006 sec and rate is 
3.6977287551e-012 sec/sec.

Entire output of the message is - 30,30,7.45629999999e+004,-
1.1858809451e+007,-
2.1249722627e+007,1.1326906314e+007,1.1932198375e+003,7.7622948298e+002,2.7
047409217e+003,1.3294251003e-006,3.6977287551e-
012,4,4.0960000000e+005,1.0816000000e+004,1.6134907007e+000

These values don't seem to be out of line with the other SV being 
tracked.  Just wondering if the clock bias has drifted this far off and 
drift now 2 orders of magnitude worse than when you made your observations?

Regards,
Skip Withrow








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