�� . �� : http://www.naic.edu/~phil/usrproj/isee3/tonedrift.html
�� : Fri Jun 13 02:56:03 2014
�� : Mon Apr 11 04:56:28 2016
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isee3 tone drift

ISEE3 carrier drift

Notes:
06jun14:added 06jun14 data.. no change in tone frequency during command sequence.
05jun14: redid data,plots using S17 ephemeris

Intro

The isee3 satellite has 2 transmitters

2217.5 Mhz (transponder B)
2270.4Mhz (transponder A)

There is a separate oscillator for each transponder. These oscillators will have drifted from the nominal frequencies.
I was interested in looking at the error in the oscillators as well as the velocity error in the ephemeris,.
The processing was:

measured the received tones
The frequency resolution used was about 1.2 hz.
doppler correct it using the velocity from the ephemeris
compute freqMeasured - (tx0Freq Doppler corrected using ephemeris)

The plot shows the freq error after Doppler correction (using the ephemeris) (.ps) (.pdf)

Let FreqErr=Measured Frquency - doppler corrected freq (using ephemeris)
top: transponder B 2217.5 freqErr
2nd: transponder A 2270.4 freqErr.
3rd: FreqerrA/FreqErrB
Bottom: Shows the difference in the satellite transmit oscillator errors.

22may14: jump in 2217.5 tone after first file

the pointing was updated after the first file. The signal went from 7db to 50 db above the noise floor. The1st freq is probably off.

28may14: there is a drift in the 2217.5 and the 2270.4 tone starting with the 3 file

transponder A drifted by 60 hz in 1.4 hours
Transponder B drifted by 6 hz

06jun14: no change in frequency when we commanded coherent mode.

What can the frequency measurements tell us:

Terminology:

name	equation	Notes
F0a	constant	2270.4e6 hz . the nominal frequency
F0b	constant	2217.5e6 hz
Da(t)	?	drift in oscillator A
Db(t)	?	drift in oscillator B
Ftxa	F0a + Da	transmitted freq A
Ftxb	F0b + Db	transmitted freq B
Veph	ephmfile	velocity from ephemeris file
Verr	?	error in ephem vlel
V	Veph + Verr	correct velocity. (neg is approaching)
Frcva	Ftxa(1-V/C)	received frequency
FrcvB	Ftxb(1-V/C)
FErcva	FrcvA-F0A(1-Veph/C)	remove doppler corrected freq (using ephemeris) from received freq.This is what was plotted above.
FErcvb	FrcvB-F0b(1-Veph/C)

We measure the received frequency and then compute FErcvA using the ephemeris file.

Expanding FErcvA gives:

FErcvA = FrcvA- F0A(1-Veph/C)

=(F0a + Da)(1-V/C) - F0a + F0a*Veph/C
=F0a - F0a(Veph + Verr)/C + Da - Da(Veph +Verr)/C - F0a + F0a*Veph/C
= -F0a*Verr/C + Da (1 -(Veph+Verr)/C)

FErcvA - Da(1-(Veph+Verr)/C) = -F0a*Verr/C
Using transponder B gives:
FErcvB - Db(1-(Veph+Verr)/C) = -F0b*Verr/C
dividing the two equations gives FEratio

K= F0A/F0B=1.02386=(FErcvA - Da(1-(Veph+Verr)/C))/
(FErcvB -Db(1-(Veph+Verr)/C))

FErcvA is about -9800 Hz
FErcvB is about -7000 Hz
The velocity (from the ephemeris) is -2 to -4 km/sec

so (Veph + Verr)/C ~ 1e-5 can be ignored relative to 1..
K=1.02386= (FErcvA - Da)/(FErcvB - Db)

Putting the oscillator errors on one side give:

K*FErcvB -FEa = (K*Db - Da)
plotting this shows the difference in the oscillator errors.

fitting for the Da,Db oscillator errors

0. =(FErcvA(t) - Da(t))/(FErcvB(t) - Db(t) - 1.02386
if the oscillator changes slowly we might fit for Da(t),Db(t)

processing: x101/projects/isee3/plottonedrift.pro

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