p3094: position switching using lbw.
p3094 did 300 sec on/off position switching
covering all of lbw using the wapp spectrometers (it also used puppi
for fast dumping).
data was taken on:
On,off position switch data was taken 3:00 to
5:00 am (AST).
The setup was:
- lbw receiver. Covering the entire band
- wapp backend, 100 MHz bands, cover entire band. 1 second
dumps, 3 level sampling.
Processing the data:
- The average spectra for each on source was computed.
- Each 300 sec on/off pair was processed
- data was scaled to Tsys (didn't want rfi in cal to
- For each 300 sec on scan the rms/mean by channel was computed
- this does a better job of showing channels that have rfi.
- the tracks for different GNS (Global Navigation Satellites)
across the dish were plotted for this time range
- galileo - 4 satellites visible
- glonass - 9 satellites visible
- beidou - 3 satellites visible (chinese gns constellation).
- gps - 10 satellites visible
- The angle between each gns satellite and the telescope beam
was also plotted.
Plotting the data:
There were 9 on/off pairs of
data taken on source.
Each wapp band is plotted in a different color.
Average 300 sec on scan spectra (.ps)
- 3 on scans per page
- Each band was normalized to its median value. No band pass
correction was done.
- I've averaged polA and polB
300 sec On/off position switched
averages (.ps) (.pdf)
- 3 on/off pairs per page
- The vertical scale is in units of Tsys
- PolA and polB have been averaged.
- The expected rms Noise in a 300 second integration, 100 MHz
bw, 4096 channels, hanning smoothing, polAdding, sinx/x
channels, 3 level sampling:
- bwEff=100E6/4096 *1.208(sinx/x)*2.25(hanning)=66 Khz
- 3level noise: 1.23
- on/off division : sqrt(2).
- tmOn=300. (on or off)
- deltaT/T =sqrt(2.)* 1.23/sqrt(bwEff * npol*tmOn) =
- The vertical scale is +/- .1 Tsys to show the rfi
rms/mean by channel for each on scan
The orbits of the GNS constellation
during this period (.ps) (.pdf)
- rms/mean was done for each freq channel of each on scan.
- The expected rms (deltaT/T) -
- 1.23/sqrt(bwEff*1.sec * 2pol)= .003 Tsys.
- For some of the cleaner bands, the rms was .0035 Tsys.
- The two line elements sets from 21oct16 were used (so they
should be pretty close).
- each visible satellite is plotted in a separate color.
- The vertical axis is the AO za for the satellite.
- The horizontal axis is the AO source azimuth of the satellite.
- points are separated by a few minutes in time (but the spacing
is not uniform in time).
- The satellite name is on the right. the date yymmdd and time
hhmmss (ast) for the lowest AO za is printed on the right
- Page 1: Galileo satellites. 4 visible
- Page 2: Glonass satellites: 9 visible
- Page 3: Beidou satellites: 3 visible
- Page 4: GPS satellites: 10 visible.
The angle between the satellites and
the pointing direction for the AO telescope (.ps) (.pdf)
- This was just done for the on scans.
- The difference was computed from the satellite ra,dec J2000
and the J2000 pointing direction of the telescope.
- The angles are great circle.
- I clipped the vertical scale to 40 degree separation. the
table below shows some of the closest approaches:
- E5A 1164-1189
- E5B 1189-1214
- E6A,E6B 1260-1300
- E2 1559-1563
- L1 1563-1587
- E1 1587-1592
spectra of scan 54: 04:43:51 ast
Dynamic spectra were made of the on source scan (300 1 sec records).
The processing was:
- the on scan was used (300 1 sec recs)
- I split the display into 2 separate images (bands 1,2,3) and
- This scan included gps L3 at 1381
- the images were flattened by the median bandpass.
- The images were scaled to about 2 sigma (to show weaker
dynamic spectra bands 1,2,3 (.gif)
dynamic spectra bands 4,5,6,8 (.gif)
Identifying the rfi:
- 1174MHz. gps or galileo L5
- 03:26 strongest. probably gps 27. present at a low level
- 1207: beidou or galileo
- 03:26 strongest: beidou M2 satellite. 5
degrees from beam.
- 1367: beidou
- 03:26 strongest. beidou M2 satellite. 5 degrees from
- 1381: gps l3
- 1575: gps or galileo
- 03:26 strongest. probably gps 27
- 1602: glonass
- 04:55 strongest. cosmos 2461. within 2deg of beam.
- 1620: iridium
- 1228,1243,1279,1294 : punta salinas mode A
- 1252,1257 1344,1349 FAA
- 1269.4,1275.6,1327.4, 1332.5 Punta borinquen radar.
- strong rfi was seen from the chinese beidou satellite at 1207
and 1268MHz,. It passed within 5 degrees of the main beam.
- The dynamic spectra showed that the gns satellites plus the
radars is making it very difficult to do measurements 1170-1300
- It would be helpful to pick an observing time when
satellites are not close to the main beam.
- the wapps 100 MHz bw use a 3 level sampler. strong signals
will spread in frequency more because of this.
- The mocks (with their 12bit samplers and pfb will do a
better job of limiting the spread of strong rfi (but of
course they still have their problem of jumps a power of 2^n
from butterfly underflow)