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Mro On Approach, TCM-3 not required
Rakhir
post Mar 10 2006, 08:02 AM
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Watch Mars Reconnaissance Orbiter's Doppler Plot in real time during MOI !
http://marsprogram.jpl.nasa.gov/mro/mission/tl_doppler.html


Mars Orbit Insertion - Sequence of Events
http://marsprogram.jpl.nasa.gov/mro/mission/tl_moi-soe.html
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Borek
post Mar 10 2006, 08:20 AM
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QUOTE (Rakhir @ Mar 10 2006, 09:02 AM) *
Watch Mars Reconnaissance Orbiter's Doppler Plot in real time during MOI !
http://marsprogram.jpl.nasa.gov/mro/mission/tl_doppler.html
Mars Orbit Insertion - Sequence of Events
http://marsprogram.jpl.nasa.gov/mro/mission/tl_moi-soe.html


Why is the small version of the Doppler plot different from the large one?
And what is the discontinuity?

Borek
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mhall
post Mar 10 2006, 11:03 AM
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I don't think the small one is live - at least, it hasn't changed in some minutes.

The discontinuity was labelled 'DSS 15 Handover' - I suppose this is when the DSN reception is being passed from one dish to the next.

Due to the rotation of the Earth, any given dish will have some additional velocity towards Mars as it (Mars) appears above the horizon; When Mars sets, the DSN dish is moving away from Mars at a similar velocity.

This means that the DSN station doppler is added to the MRO doppler; the DSN doppler is at its strongest, but in opposite directions, at handover.

Anyway, that's my take on it.

--Martin
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MERovingien
post Mar 10 2006, 11:52 AM
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Hi everybody!

New to this board, although I have been lurking through these pages since the very beginning.

I have been bitting my nails on my own on MODY's MOI in 2001, then again for Spirit's and Oppy's arrival in 2004. So today, on MRO's MOI I have chosen to bite my nails in good company. In excellent company.


Go MRO!!
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The Messenger
post Mar 10 2006, 03:14 PM
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QUOTE (Rakhir @ Mar 10 2006, 01:02 AM) *
Watch Mars Reconnaissance Orbiter's Doppler Plot in real time during MOI !
http://marsprogram.jpl.nasa.gov/mro/mission/tl_doppler.html
Mars Orbit Insertion - Sequence of Events
http://marsprogram.jpl.nasa.gov/mro/mission/tl_moi-soe.html

Utterly cool.

We are seeing a sawtooth in the residuals @ ~6 minute intervals - is this due to attitude control, solution harmonics or what?
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jmknapp
post Mar 10 2006, 05:01 PM
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QUOTE (The Messenger @ Mar 10 2006, 10:14 AM) *
Utterly cool.

We are seeing a sawtooth in the residuals @ ~6 minute intervals - is this due to attitude control, solution harmonics or what?


Interesting item from 2001 Mars Odyssey orbit determination during interplanetary cruise:



The resolution of the graph makes it hard to read, but it look like the amplitude of the sawtooth is a bit larger than with MRO (~5x), and the period about 15 minutes.

QUOTE
During the TCM-2 data arc, a couple passes of Doppler
residuals such as that shown in Figure 5 exhibited a
peculiar sawtooth pattem. Because it appeared that we
were having problems fitting the data without the gasleak
acceleration estimation, we became concerned that
this may have been more evidence of serious problems
in the SIC modeling, the SDST, DSN hardware or the
ODP. Several DSN and NAG experts helped analyze
these unusual patterns, but no definitive explanation
was found. The DSN tracking procedures for Odyssey
had been to follow the S/C’s downlink frequency within
a fairly tight bandwidth by periodically ramping the
uplink signal. It was believed that this ramping of the
signal could have contributed to this problem,
especially if the values of the ramp rates were being
truncated, but no evidence of this was found. In the case
that this data was incorrect, our procedures were to
remove the data, however, it was determined that the
data had little effect on the OD solutions, especially due
to the signatures’ high fi-equency nature.


--------------------
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Rakhir
post Mar 10 2006, 05:14 PM
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There was a final TCM planned (if needed) at 15:24 UTC.
No change is visible on the doppler, so I guess it was cancelled (or too small to be seen).

-- Rakhir
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djellison
post Mar 10 2006, 05:16 PM
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Press conf is on now - they did no TCM5

Doug
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The Messenger
post Mar 10 2006, 05:40 PM
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QUOTE (jmknapp @ Mar 10 2006, 10:01 AM) *
Interesting item from 2001 Mars Odyssey orbit determination during interplanetary cruise:



The resolution of the graph makes it hard to read, but it look like the amplitude of the sawtooth is a bit larger than with MRO (~5x), and the period about 15 minutes.

Thanks - this is a good read, and the unmodel aspect - small forces corrections - required to hit the target make the cancelation of the finally 3-4 corrections very impressive navigation!

Oh, and the saw tooth? Still an unsolved mystery:)
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jmknapp
post Mar 10 2006, 05:55 PM
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Comparing two NASA MRO prediction kernels, one for ideal MOI and one for no MOI, gives these predicted times (Earth-received UTC):

loss-of-signal: 21:46:09 MOI, 21:46:09 no-MOI (no difference)
aquisition-of-signal: 22:16:00 MOI, 22:08:56 no-MOI (no-MOI AOS being 7:04 earlier)

So when looking at the doppler plot, LOS should happen at 21:46:09 UTC regardless, and hopefully AOS will not be before 22:16:00 UTC. The time between 22:08:56 to 22:16:00 would be the critical time. I suppose that anything much after 22:16:00 would indicate too much of a burn.


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yaohua2000
post Mar 10 2006, 06:14 PM
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Mars Reconnaissance Orbiter was only 50000 kilometers away from Mars at 2006-03-10 17:25:55 UTC.

velocity = 3.111 km/s
range-rate = -3.082 km/s
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Nix
post Mar 10 2006, 06:57 PM
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Hi guys, can I join the party?

-sitting on edge of seat for the coming hours as you all are I'm sure smile.gif

Nico


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photographer, space imagery enthusiast, proud father and partner, and geek.


http://500px.com/sacred-photons &
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djellison
post Mar 10 2006, 07:10 PM
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Feel free to join the rave smile.gif

http://www.unmannedspaceflight.com/index.p...view=getnewpost

There's a big crowd..well.....3 of us smile.gif

Doug
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mhall
post Mar 10 2006, 07:18 PM
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Don't worry, we'll be watching when the time comes.
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Joffan
post Mar 10 2006, 07:24 PM
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3 is a crowd, anyway.

So that's three TCMs all unneeded leading up to an orbit insertion burn. That is just an awesome performance, and if I were superstitious (which I'm not, touch wood) I would hope we haven't used up our luck early. wink.gif
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