The RTDC
Processing SMA Data
1.2 m Telescopes
AST/RO
Extra

An Introduction to SMA Data Reduction


Useful links before you start

What are the files in the SMA data directory?
SMA Data FAQ
Getting an overview of your data


Reducing the size of your data

The SWARM correlator has a fixed bandwidth and resolution, so file sizes in excess of 100GB are increasingly common. You may wish to reduce the size of your data file by rebinning the spectral data cube. This is especially important if you plan to use MIR, as it has a memory requirement of 2-3x the data size. The SMA provides a custom tool for rebinning SMA data: SMARechunker. You can expect the data size to scale linearly with the rebin factor.

Reducing the Size of your Data
Using SMARechunker


Calibrating SMA data

We currently recommend using MIR, an IDL based package tailored for the SMA, to calibrate your data. This is well supported at the CfA and expertise is available. MIR only performs calibration steps, however data can be written out in either MIRIAD or uvfits format, allowing MIRIAD or CASA to be used for cleaning and imaging.

SMA Data Calibration with MIR/IDL
The MIR Cookbook

CASA can be used for calibrating SMA data, however, it can be very slow, and there is currently no fully supported path for converting raw SMA data to CASA MS format. The available options can be found at Converting SMA data to CASA MS format, but we cannot guarantee their efficacy.

A CASA tutorial on the reduction of SMA data is available (see link below). This example uses data that has been Tsys corrected and written out as uvfits from MIRIAD. Be warned that this, and other, examples may not be compatible with newer versions of CASA.

SMA CO Line Data 3.2 (NRAO tutorial)

MIRIAD too is capable of calibrating SMA data, however, we do not recommend it. While MIRIAD is reasonably reliable at reading ASIC data (pre-2016), it more often than not encounters errors reading SWARM data. If you chose this route you can find information on the MIRIAD home page.

Polarization data requires specialized tasks which are available in both MIR and MIRIAD. If you wish to reduce polarization data please email smarequester@cfa.harvard.edu for assistance.


Imaging SMA data

MIRIAD or CASA can used to image SMA SWARM data, with most users preferring CASA. However, we do not recommend using CASA for imaging older ASIC data. Data calibrated with MIR can be written out in MIRIAD format, or uvfits format for CASA.

SMA Data Reduction with MIRIAD (RTDC)
MIRIAD Software for SMA (SMA)
SMA Data Reduction with CASA (RTDC)
SMA CO Line Data 3.2 (NRAO tutorial)


Summary

MIR/IDL
MIRIAD
CASA
AIPS
Calibration
Imaging✔‡
Can read raw SMA data✔*✔†
Well supported
(Recommended)
‡ SWARM data only
* ASIC data only
† Not fully supported

MIR, MIRIAD and CASA are all available from the RTDC, CF and Hilo machines. AIPS is available from the RTDC only.


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