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#20
by
Comga
on 16 Mar, 2011 19:43
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How does the precision of today's landing of TMA-M compare to previous flights?
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#21
by
anik
on 19 Mar, 2011 09:22
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Soyuz TMA-M:
Planned point specified after undocking - 51°01' N, 67°13' E; 88 km N of Arkalyk.
Actual point - 51°02'54" N, 67°17'36" E; 93 km N of Arkalyk.
Overshoot - 6 km NE.
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#22
by
patchfree
on 19 Mar, 2011 12:59
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Soyuz TMA-M:
Planned point specified after undocking - 51°01' N, 67°13' E; 88 km N of Arkalyk.
Actual point - 51°02'54" N, 67°17'36" E; 93 km N of Arkalyk.
Overshoot - 6 km NE.
Can this overshoot be explained by the high winds during the parachute phase or by the precision limits of the spacecraft guidance during the "gliding" phase?
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#23
by
AnalogMan
on 19 Mar, 2011 13:03
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Soyuz TMA-M:
Planned point specified after undocking - 51°01' N, 67°13' E; 88 km N of Arkalyk.
Actual point - 51°02'54" N, 67°17'36" E; 93 km N of Arkalyk.
Overshoot - 6 km NE.
I updated my scatter graph with this latest data point (marked in red) - click to enlarge.
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#24
by
Comga
on 24 May, 2011 05:41
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Waiting for today's landing to be added to the database...
Looked really close to the ground observers, with little wind
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#25
by
Comga
on 23 Jun, 2011 14:51
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Waiting for today's landing to be added to the database...
Looked really close to the ground observers, with little wind
Bump
Are the target and actual coordinates available?
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#26
by
anik
on 23 Jun, 2011 17:15
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Are the target and actual coordinates available?
47°19' N, 69°35' E
47°21'57.84" N, 69°27'49.26" E
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#27
by
AnalogMan
on 26 Jun, 2011 10:38
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Are the target and actual coordinates available?
47°19' N, 69°35' E
47°21'57.84" N, 69°27'49.26" E
Updated my scatter graph with this latest data point for TMA-20 (marked in red) - click to enlarge.
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#28
by
NotGncDude
on 26 Jun, 2011 20:34
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If I weren't so lazy I'd love to do a downrange-crossrange dispersion aligned with the ground track. You should expect to see much smaller crossrange error... should.
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#29
by
Comga
on 29 Jun, 2011 20:31
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Are the target and actual coordinates available?
47°19' N, 69°35' E
47°21'57.84" N, 69°27'49.26" E
Thanks!
I get a 9.8 km offset of actual from target. This is right around the median of all previous flights, although it lies in the otherwise unoccupied North-West quandrant of AnalogMan's graph. Was it unreasonable to expect the new digital control system to reduce the distance?
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#30
by
Danderman
on 29 Jun, 2011 21:32
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Are the target and actual coordinates available?
47°19' N, 69°35' E
47°21'57.84" N, 69°27'49.26" E
Thanks!
I get a 9.8 km offset of actual from target. This is right around the median of all previous flights, although it lies in the otherwise unoccupied North-West quandrant of AnalogMan's graph. Was it unreasonable to expect the new digital control system to reduce the distance?
The new digital control system is only used on orbit; otherwise, the landing computer is the same one used by Soyuz TMA. Some day, the digital unit may be installed in the descent module. Some Day.
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#31
by
Comga
on 30 Jun, 2011 16:25
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Are the target and actual coordinates available?
47°19' N, 69°35' E
47°21'57.84" N, 69°27'49.26" E
Thanks!
I get a 9.8 km offset of actual from target. This is right around the median of all previous flights, although it lies in the otherwise unoccupied North-West quandrant of AnalogMan's graph. Was it unreasonable to expect the new digital control system to reduce the distance?
The new digital control system is only used on orbit; otherwise, the landing computer is the same one used by Soyuz TMA. Some day, the digital unit may be installed in the descent module. Some Day.
Thanks for the information.
A better calculation (and a check on my arithmetic) yields 10.56 km, slightly above the median offset distance.
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#32
by
anik
on 16 Sep, 2011 18:14
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Soyuz TMA-21:
Planned point specified after undocking - 47°18' N, 69°35' E; 151 km SE of Dzhezkazgan.
Actual point - 47°19'11.6" N, 69°30'06.8" E; 144 km SE of Dzhezkazgan.
Undershoot - 6.5 km NW.
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#33
by
AnalogMan
on 16 Sep, 2011 22:13
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Soyuz TMA-21:
Planned point specified after undocking - 47°18' N, 69°35' E; 151 km SE of Dzhezkazgan.
Actual point - 47°19'11.6" N, 69°30'06.8" E; 144 km SE of Dzhezkazgan.
Undershoot - 6.5 km NW.
Updated my scatter graph with Anik's latest data point for TMA-21 (marked in red) - click to enlarge
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#34
by
asdert
on 14 Nov, 2011 13:13
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I noticed something odd in the data. Until TM-27, all data is in integral units of minutes of latitude and longitude. After that, the "planned" remain rounded but the "actuals" are usually in integral units of seconds of latitude and longitude
Planned coordinates are always given in rounded minutes. Actual coordinates can be rounded to minutes or have seconds - it depends on equipment used for determination of coordinates. Now we are using GPS data for determination so coordinates have seconds.
I wonder whether all coordinates are given in the same reference system. Google Maps uses WGS84, doesn't it? While modern GPS devices may be set to that reference, I guess that in the Soviet era they rather used the Pulkovo datum, but the given numbers don't suggest they have been converted to WGS84.
Is the difference so small that it can be neglected?
When calculating the landing error, the planned and the actual landing coordinates should be given in the same system, otherwise it makes no sense to calculate differences.
What is the current official coordinate system in Russia and Kazachstan?
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#35
by
asdert
on 17 Nov, 2011 11:18
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Is the difference so small that it can be neglected?
Okay, I think after some research and calculation I can answer my question myself:
It looks like the difference between the Russian system and the International system is around 100 metres or 3 arc seconds in latitude.
For the desert of Kazakhstan, this is quasi zero.
When comparing planned to actual position, it is a rather small value that can be neglected, seen the precision of the input values.
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#36
by
anik
on 25 Nov, 2011 17:01
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Soyuz TMA-02M:
Planned point specified after undocking - 51°03' N, 67°09' E; 90 km N of Arkalyk.
Actual point - 51°02'55.08" N, 67°11'03.54" E; 91 km N of Arkalyk.
Overshoot - 2.4 km E.
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#37
by
Comga
on 25 Nov, 2011 22:47
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And my version of AnalogMan's plot showing TMA-02M to have the smallest miss distance yet. (TMA-02M in red)
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#38
by
anik
on 10 May, 2012 14:28
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Soyuz TMA-22:
Planned point - 51°01' N, 67°10' E; 88 km NE of Arkalyk.
Actual point - 50°57'20.4" N, 67°09'51.8" E; 80 km NE of Arkalyk.
7 km S.
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#39
by
AnalogMan
on 10 May, 2012 19:56
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Soyuz TMA-22:
Planned point - 51°01' N, 67°10' E; 88 km NE of Arkalyk.
Actual point - 50°57'20.4" N, 67°09'51.8" E; 80 km NE of Arkalyk.
7 km S.
Updated my scatter graph with this latest data point (marked in red) - click to enlarge