SMA Data Format
The SMA data format
Raw SMA data is recorded in a variety of files contained in a single directory. The data format is MIR, which is IDL tailored to work with SMA data. The data are binary so detailed file format information is required to unpack it.
How do I change the format?
You can find details of the options at Converting SMA Data to a CASA Compatible Format. The primary package, pyuvdata, can be used to convert interferometry data between multiple supported formats. SMA data is a new addition to this package and is actively being fully incorporated.
What are all the files in the data directory?
You can find a description of the files at What's in the SMA raw data directory? As the data is binary, detailed formatting information is needed to unpack it.
What were the setup and sources for this dataset?
You have a few options for getting an overview of a dataset - including the correlator(s), sources and tuning. In addition to the options below you can check the observing report for non-proprietary data which is linked from the SMA Data Archive, or email smarequester@cfa.harvard.edu.
1) SMARechunker -L
When the spectral windows/chunks are given they will be numbered as sX. The continuum channel is c1.
$ SMARechunker -i /sma/data/science/mir_data.2021/210115_16:57:05/ -L The file has 189 scans and contains data for the following chunks: c1 s1 s2 s3 s4 s5 s6
2) whatishere
$ whatishere /sma/data/science/mir_data.2021/210115_16:57:05/
|>---------------------------------------------------------------------
LO Freq. (Rx0): 225.513 GHz
UT Start: 16.9482 UT Stop: 17.7514
Maximum baselines: 21 Max. ok baselines: 21
Minimum baselines: 21
Number of scans: 189 Number of ok scans: 189
Number of sources: 5
(In following list, names are truncated at 16 characters)
# Name #Scans Scan Range Avg UTH HA min HA max
1 vesta 2 ( 0- 1) 16.9502 2.61 2.61
2 Vesta 8 ( 2- 9) 16.9791 2.62 2.65
3 3c345 66 ( 10- 188) 17.4006 -2.38 -1.65
4 1642+398 33 ( 15- 47) 17.0714 -2.35 -2.31
5 J1653+397 80 ( 60- 175) 17.4257 -2.42 -1.89
|>---------------------------------------------------------------------
LO Freq. (Rx1): 225.513 GHz
UT Start: 16.9482 UT Stop: 17.7514
Maximum baselines: 21 Max. ok baselines: 21
Minimum baselines: 21
Number of scans: 189 Number of ok scans: 189
Number of sources: 5
(In following list, names are truncated at 16 characters)
# Name #Scans Scan Range Avg UTH HA min HA max
1 vesta 2 ( 0- 1) 16.9502 2.61 2.61
2 Vesta 8 ( 2- 9) 16.9791 2.62 2.65
3 3c345 66 ( 10- 188) 17.4006 -2.38 -1.65
4 1642+398 33 ( 15- 47) 17.0714 -2.35 -2.31
5 J1653+397 80 ( 60- 175) 17.4257 -2.42 -1.89
|>---------------------------------------------------------------------
3) IDL select command
IDL> readdata, dir='/sma/data/science/mir_data.2021/210115_16:57:05/', int=[1,10] IDL> select All Sources: vesta Vesta 3c345 1642+398 J1653+397 All Baselines: 1-2 1-3 1-4 1-5 1-6 1-7 2-3 2-4 2-5 2-6 2-7 3-4 3-5 3-6 3-7 4-5 4-6 4-7 5-6 5-7 6-7 All Recs: 230 240 All Bands: c1 s1 s2 s3 s4 s5 s6 All Sidebands : l u All Polarization states: hh vv hv vh All Integrations: 1-10
SMA Correlators - Spectral windows and chunks
The SMA has had two correlators: ASIC, and (exclusively since 2016) SWARM. ASIC had 48 spectral windows which could each have a different frequency resolution. While at different points in the array's history, ASIC has had 2GHz or 4GHz bandwidth. SWARM on the other hand is more straightforward. It has just six chunks (SWARM terminology for spectral windows) of 2GHz each, with a fixed frequency resolution of 140kHz. The transition from ASIC to SWARM was gradual with overlap between 2014 and 2016.
| CORRELATOR | DATES | DETAILS | NOTES |
|---|---|---|---|
| ASIC | 2003-2016 |
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| SWARM | 2014-2020 |
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| SWARM | 2021-present |
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SWARM (2021)
ASIC
