S2462 radar moon test
30jan09
jan09
s2462 used the sband
transmitter to transmit a low power signal to a satellite orbiting the
moon. Transmission occurred on 30jan09.
The plots show the
az,za and ra,dec positions of the telescope during the test (.ps) (.pdf):
- Page 1: az,za positions during the test
- Top: az vs hour of day (utc).
- middle: za vs hour of day (utc).
- bottom: za vs az for the test.
- Page 2: ra,dec positions during the test
- The ra,dec positions are epoch of date (current).
- top: ra vs hour (utc) of day
- middle: dec vs hour (utc) of day
- bottom: Ephemeris position - measured position vs hour (utc) of
day.
- The difference is great circle arc seconds (the ra dif has
been multiplied by the cosine of the dec).
List of coordinate positions by second
during the test:
processing: x101/090130/rdrcoord.pro
aug09: LRO
Tests were done with the lro satellite orbiting the
moon during aug09. The dates were:
- 16,17,20 aug09: Ao transmits, lro receives.
- 21aug09: Ao transmits,lro receives followed by lro transmits and
ao receives.
Telescope pointing 16,17,20,21 aug09
The plots show the az,za position of the ao
telescope during the tests as well as the difference between the
telescope position and the ephemeris requested position. A datafile is
also included for each day giving the measured ao positions for each
day (utcSec, ra,dec of date).
processing:16aug09:rdrcoord.pro
21aug09: Measure lro stokes V: lro xmit, ao Receives
Links to plots:
cal
on/off samples averaged to 1 seconds (.ps) (.pdf)
the
average spectral density during the cal measurements (.ps) (.pdf)
total
power over the 500 Khz band to compute stokesV (.ps) (.pdf)
compute
stokes V using the frequency channel of the max value in polB (.ps)
(.pdf)
On 21aug09 lro transmitted and
then ao Received
during the second part of the experiment (the first half had AO
xmitting and lro receiving). The AO receive setup was:
- Use sband Narrow (native circular via a turnstile).
- place 10db pads before and after the post amp chassis.
- Record 500 Khz complex baseband data for both polA and polB using
the 12 bit a/d converters of the RI.
- This band was centered at 2380 MHz.
- Note: PolA is right hand circular
and polB is left hand circular (ieee convention)
- We did not doppler track the lo's during the experiment so the
frequency of the xmit signal of the satellite will drift due to
the doppler change.
- The receive cycle was done toward the end of the pass when
the za was close to the limit (19 deg).
- After the receive cycle completed (and the satellite was no
longer being tracked, we fired the cal noise diode.
- it was 1 second on, 1 second off. This was repeated about 28
times.
- The moon was still in the beam during the firing of the noise
cal.
The cal on/offs:
The first set of plots shows the cal on/off samples averaged to 1 seconds
(.ps) (.pdf):
- Page 1: calOn (black), calOff (red)
- top: polA, bottom polB
- The 1 second averages excluded the transition region of the cal.
- The power decreases with cal measurement. This is because the
telescope was sitting at 19.6 degrees za and the moon was drifting out
of the beam.
- The vertical axis is 2* a/d^2 .
- PolB has a low level 80-> about 6 counts/sigma. The strong
xmitted signal was arriving in polB. It had about 10db more attenuation
than polA. When the xmitted signal went away, the input powers were
equal so polB levels came out lower.. The Cal measurement still looks
like it worked ok... Next time we should adjust the power levels with
the xmit signal off, put in an extra 10 or 20 db, and then take data...
- Page 2:
- top,middle: cal scale factors for polA, polB. This shows the 28
separate cal on/offs taken. The green line is the median value
for each. This was used to convert a/d^2 to Kelvins.
- Bottom: Tsys for the cal off measurements. Black is polA, red
is polB
- Tsys was about 200K. It decreased towards the end because the
moon was drifting out of the beam.
The second set of plots shows the average spectral density during
the cal measurements (.ps) (.pdf):
- Top,Middle is the average spectra for polA, polB smoothed to 120
Hz resolution. The Tsys includes 1/2 the cal value of 6 Kelvins (since
i averaged over the cal on and the cal off).
- Bottom: blowup +/- 1Khz about DC.
- There is strong 60 hz in polB. This is because the signal level
was low do to the extra 10db attenuation.
Stokes V
The first set of plots uses the total power over the 500 Khz
band to compute stokesV (.ps) (.pdf):
- Page 1: polA,B and stokesV. The time is ast hours (gmt-4).
- This data was taken during the satellite transmit.
- Top,middle: polA,poB
- Bottom: stokes V
- Defined as (polB-polA)/(polB+polA) or ( LC-RC)/(LC +
RC) (according to Kraus radio astronomy pg 123 this is the correct
sign).
- So the signal is about 97.5% circular.
- Page 2: 4 second oscillation:
- The recevied signal showed a 4 second oscillation in time of a
few percent. it is seen in both polA and polB. This does not correspond
any of the resonant
frequencies of AO.
The Second set of plots compute
stokes V using the frequency channel of the max value in polB (.ps)
(.pdf):
- 2 Hz resolution was used for the transforms (256K * 2usec ).
- Page 1: the average spectra during ao rcv.
- top: polA
- 2nd: polA blowup showing sidebands
- 3rd: polB
- bottom: polB blowup showing sidebands
- The vertical scale for polB is about 100 times polA.
- Page 2: Blowup of average spectra around the transmitted tone.
- The smearing is caused by the doppler. It was moving by about 1
channel (2hz) in each spectra (.5 secs).
- Page 3:
- top. the frequency of the peak (offset from 2380 MHz) vs time.
This is from the change in doppler.
- bottom: Stokes V for the spectral channel of the peak in polB.
The signal a the peak is 97.6 % circular.
processing: x101/090821/lro_cal.pro,
lro_proc.pro
home_~phil