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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 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-Jan 2015
  • 2GHz bandwidth.
  • 48 spectral windows, each of which could have a different number of channels.
  • The spectral windows are labeled s01-s48.
  • Some windows may be missing from certain data.
SWARM
+
ASIC
Jan 2015 -  Sep 2016
  • Adds SWARM chunks to the old 2GHz ASIC correlator.
  • Fixed frequency resolution of 140kHz for SWARM. Variable resolution for ASIC.
  • The first 4 SWARM chunks were added two at a time from 150114. Their labels were appended to the ASIC numbers as s49-s52.
  • s49, s50: 150114 - 160212
          s49, s50, s51, s52: 160213 - 161006
  • The data from the early days of SWARM was test quality only and you will want to check the quality.
SWARM
4 chunks
Oct 2016 - Aug 2020
  • 4 chunks at 2GHz bandwidth each per sideband.
  • Maximum potential bandwidth of 32GHz.
  • Fixed frequency resolution of 140kHz.
  • ASIC was switched off on 161007 leaving only SWARM data.
  • When ASIC was turned off the 4 SWARM chunks were relabeled s1-s4.
SWARM
6 chunks
Aug 2020 - present
  • 6 chunks at 2GHz bandwidth each per sideband.
  • Maximum potential bandwidth of 48GHz.
  • Fixed frequency resolution of 140kHz.
  • The new chunks s5 & s6 were added on 200825 in a shared-risk capacity.
  • s5 and s6 officially come online Jan 19 2021.
  • The sensitivity of the new chunks falls off at higher frequencies, especially towards the upper edge of the bands.


SWARM (2021)


ASIC