class-weighting

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IRAM Memo 2021-?
Weighting scheme in CLASS
S. Bardeau, J. Pety
1. IRAM (Grenoble)
2. Observatoire de Paris
April, 7 2021
Version 1.0

### Abstract:

The weighting scheme of CLASS was slightly inconsistent when summing or averaging spectra observed in different observing modes (frequency switching, wobbler switching, and position switching). A first attempt at solving this problem that was implemented on Sep. 17th, 2019, led to incorrect system temperatures in the output spectrum when averaging or summing folded frequency switched spectra. This in turn brake the associativity of the average or sum commands: When averaging three folded frequency switched spectra S1, S2, and S3, the noise level of (S1+S2+S3) was slightly different from the noise level of ((S1+S2)+S3)).

In this memo, we describe the problem and propose a solution that was implemented in the mar21 release of GILDAS. We ask all our users that currently use a version of GILDAS between oct19 and feb21 to update their version to the newest one.

Keywords: CLASS Data Format

Related documents: Averaging spectra with CLASS (memo 2009-4), MRTCAL user manual.

- Contents
- Weighting modes
- Switching modes
- Fixing folded frequency switching weight
- Fixing the `AVERAGE` output system temperature
- Consequences
- Test data
- About this document ...