VEGAS Commissioning Memo Data Reduction Notes
Introduction
This page is for shared work on the data reduction for the VEGAS commissioning memo. Eventually, the contents should transfer pretty painlessly into the memo.
Commissioning data consists of:
- Engineering Tests (Anish)
- Ripple Tests (Amanda)
- Astronomical Tests (Richard, Sam, Adam)
- RRL tests
- Continuum Tests
- Deep integration tests
GBIDL and python for these tests should be kept around - they will form the basis of long-term unit / regression tests.
To Do List For Astronomical Tests
- Priority order is TP on W3, TP on 3C147, FSW on W3, long integration.
- create a shared SDFITS file with all of the observations
- create a GBTIDL to flag the center channel of every ifnum and plnum of every scan, before we do any other processing. Is it N/2 or N/2+1 ?
- run getps or getfs and look at every scan, ifnum and plnum - need a procedure to run through all of these.
- inspect every plot visually, but only print out discrepant ones
- make a note of RFI (I have seen something that looks like that), duff scans (maybe Bank H), etc
RRL Scans
- Get Tsys for every scan, ifnum and plnum - put in a database. Plot histograms of this. Plot against elevation.
- do we need to do this for every integration? I hope not!
- Get rms for every scan, ifnum, plnum. Compare to radiometer equation. Plot histograms of this.
- create a routine to fit a baseline and Gaussian for every scan, ifnum and plnum.
- create a database of frequency and intensity for all RRLs. Compare to established values
- Do above for TP and SP
3C147 scans
- Get Ta as a function of frequency for all windows, etc.
- Plot against spectral index of 3C147. Deduce scatter in intensity measurements.
Deep Integrations
- Plot Tsys, Trms and Tline as a function of integration time
Commissioning Memo
Introduction.
Observations were made using VEGAS and the X-band (8-10 GHz) receiver of a number of radio recombination lines (RRL) in W3, as well as two calibrators, 3C147 and 3C395. A source position of 02:25:44.40, +62:06:11 (J2000) and an LSRK velocity of -40.9km/s
was used (Dana Balser, private communication).
The majority of the observations were made over the weekend of 18 - 20th July, with observations running from noon until 10pm. Some additional observations were made later in the month, to fill in some data which had been lost due to faults. During all of the observation periods, the weather was poor, with the sky completely overcast, and occasional light rain.Observations were made with the active surface turned on, and Peak / Focus observations were made (on calibrators chosen by AutoPeakFocus) every one-two hours. A log of observations is given in Table 1. Data were "filled" using sdfits-test, version 1.20.
A "typical" position-switched spectrum is shown in Figure 1. This was made in Mode 25, and only one of 64 windows (covering the H89alpha line) is shown, Typical off-source system temperatures were ~ 30k (to be confirmed by Sam), and on-source system temperatures 85K 9to be confirmed). Typical observations were made with five minutes Off, and five minutes On, with the offset chosen so that the telescope would follow the same (az,el) trajectory in each case.
- Scan 6 position-switched plot plot of a typical position-switched scan. No processing has been performed on the data apart from that applied by the GBTIDL "getps" command.
Observations were made in modes 3 through 29, with the exceptions of modes 14 and 19, which were not available at the time the observations were made (
list ones we didn't use in 20-29. We went bacl and did 1-3, for what?) For single-subband modes, each of the eight spectrometer banks was tuned to a different line, using a scheduling block provided by Dana Balser. For eight subband mode, the 64 subbands of the eight spectrometers were tuned to 64 different lines. The relevant scheduling blocks are attached here:
BOF files
The BOF files (FPGA personalities) in use at the time of the observations were as follows:
Mode |
BOF file |
1 |
h1k_ver108_1500_2014_Jul_15_0006.bof |
2 |
h16k_ver110_2014_Apr_08_1753.bof |
3 |
h16k_ver110_1080_2014_Jul_15_0728.bof |
4 |
l1_ver116_1500_2014_Jul_16_0619.bof |
5 |
l1_ver116_1500_2014_Jul_16_0619.bof |
6 |
l1_ver116_1500_2014_Jul_16_0619.bof |
7 |
l1_ver116_800_2014_Jul_16_0616.bof |
8 |
l1_ver116_800_2014_Jul_16_0616.bof |
9 |
l1_ver116_800_2014_Jul_16_0616.bof |
10 |
l8_ver139_1500_2014_Jul_16_2223.bof |
11 |
l8_ver139_1500_2014_Jul_16_2223.bof |
12 |
l8_ver139_1500_2014_Jul_16_2223.bof |
13 |
l8_ver139_1500_2014_Jul_16_2223.bof |
15 |
l8_ver139_750_2014_Jul_16_2242.bof |
16 |
l8_ver139_750_2014_Jul_16_2242.bof |
17 |
l8_ver139_750_2014_Jul_16_2242.bof |
18 |
l8_ver139_750_2014_Jul_16_2242.bof |
20 |
l8_ver139_1500_2014_Jul_16_2223.bof |
22 |
l8_ver139_1500_2014_Jul_16_2223.bof |
24 |
l8_ver139_1500_2014_Jul_16_2223.bof |
25 |
l8_ver139_1080_2014_Jul_16_2244.bof |
29 |
l8_ver139_1080_2014_Jul_16_2244.bof |
Observing Log
Scans |
Source |
Mode |
Switching |
Comments |
6-7 |
W3 |
25 |
TP |
|
9-10 |
W3 |
29 |
TP |
|
11-12 |
W3 |
20 |
TP |
|
13-14 |
W3 |
24 |
TP |
|
20-21 |
W3 |
15 |
TP |
|
22-23 |
W3 |
16 |
TP |
|
24-25 |
W3 |
17 |
TP |
|
26-27 |
W3 |
18 |
TP |
|
33-34 |
W3 |
10 |
TP |
|
35-36 |
W3 |
11 |
TP |
|
37-38 |
W3 |
12 |
TP |
|
39-40 |
W3 |
13 |
TP |
|
47-48 |
3C147 |
10 |
TP |
|
49-50 |
3C147 |
11 |
TP |
|
51-52 |
3C147 |
12 |
TP |
|
53-54 |
3C147 |
13 |
TP |
|
55-56 |
3C147 |
15 |
TP |
|
57-58 |
3C147 |
16 |
TP |
|
59-60 |
3C147 |
17 |
TP |
|
61-62 |
3C147 |
18 |
TP |
|
68-69 |
3C147 |
20 |
TP |
|
70-71 |
3C147 |
24 |
TP |
|
72-73 |
3C147 |
25 |
TP |
|
74-75 |
3C147 |
29 |
TP |
|
91 |
W3 |
10 |
SP |
|
92 |
W3 |
11 |
SP |
|
93 |
W3 |
12 |
SP |
|
94 |
W3 |
13 |
SP |
|
95 |
W3 |
14 |
SP |
|
96 |
W3 |
15 |
SP |
|
97 |
W3 |
16 |
SP |
|
98 |
W3 |
17 |
SP |
|
99 |
W3 |
18 |
SP |
|
104 |
W3 |
20 |
SP |
|
105 |
W3 |
24 |
SP |
|
106 |
W3 |
25 |
SP |
|
211-212 |
W3 |
4 |
TP |
|
213-214 |
W3 |
5 |
TP |
|
215-216 |
W3 |
6 |
TP |
|
217-218 |
W3 |
7 |
TP |
|
219-220 |
W3 |
8 |
TP |
|
221-222 |
W3 |
9 |
TP |
234-235 |
3C147 |
1 |
TP |
IF Manager flaky - data may be no good |
236-237 |
3C147 |
2 |
TP |
as above |
238-239 |
3C147 |
3 |
TP |
as above |
240-241 |
3C147 |
4 |
TP |
as above |
242-243 |
3C147 |
5 |
TP |
as above |
246-247 |
3C147 |
6 |
TP |
as above |
248-249 |
3C147 |
7 |
TP |
as above |
250-251 |
3C147 |
8 |
TP |
as above |
252-253 |
3C147 |
9 |
TP |
as above |
259-278 |
W3 |
29 |
TP |
deep integration |
308-327 |
NCP |
?? |
TP |
Deep integration, mislabelled W3 |
328-343 |
NCP |
?? |
TP |
Deep integration, mislabelled W3 |
Columns: Scan number(s), Source Name, VEGAS Mode, Switching scheme (TP = total power with cal, SP = frequency switched with cal), Notes.
Comparison Spectrometer Data
Bania et al (private communication) have made similar observations as those described here, but with the old GBT Autocorrelation Spectrometer. The summary of their results is in the attached file: