Keywords: class-weighting

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# Test data

We test here the `AVERAGE` command behavior and the noise properties on a frequency switch dataset. Here we use the 3 frequency switch tracked spectra observed on 03-jun-2013, scans 100, 101, and 102, on the Vespa 4 backend part (`30ME2VLI-V04`).

Table 1: Status of the raw spectra w/t their theoretical and measured noise in all CLASS versions. is the integration time, is the frequency resolution. The theoretical noise is computed from , , and (in Hz): . The measured noise is computed by the `BASELINE` command, excluding the windows with signal.
Scan | Tsys | t |  | Theoretical noise | Measured noise | Status
| (K) | (s) | (MHz) | (K) | (K) |
100 | 224.66 | 56.61 | 0.0195 | 0.214 | 0.219 | OK
101 | 224.53 | 56.61 | 0.0195 | 0.214 | 0.220 | OK
102 | 224.40 | 56.61 | 0.0195 | 0.213 | 0.217 | OK

Table 2: Same as Table 1, for the averaged spectra produced by the command `AVERAGE` in CLASS version feb21. We combine the 3 spectra either in a single call (100+101+102), or in 2 calls with an intermediate average (100+101, then (100+101)+102). This CLASS version gives unexpected results (in red). 1) After a single average, the system temperature, and thus the theoretical noise, is underestimated by a factor , but the measured noise is correct as the weighted average used proper weights. 2) when averaging in several calls, the error on the system temperature propagates also to the weighted average; we can show that the measured noise is divided by instead of ( overestimate) after the 2-average sequence.
Average | Tsys | t |  | Theoretical noise | Measured noise | Status
100+101+102 | red158.77 | 169.84 | 0.0195 | red0.087 | 0.127 | Unexpected
100+101 | red158.81 | 113.23 | 0.0195 | red0.107 | 0.154 | Unexpected
(100+101)+102 | red122.99 | 169.84 | 0.0195 | red0.068 | red0.131 | Unexpected

Table 3: Same as Table 1, for the averaged spectra produced by the command `AVERAGE` in CLASS version mar21.
Average | Tsys | t |  | Theoretical noise | Measured noise | Status
100+101+102 | 224.53 | 169.84 | 0.0195 | 0.123 | 0.127 | OK
100+101 | 224.59 | 113.23 | 0.0195 | 0.151 | 0.154 | OK
(100+101)+102 | 224.53 | 169.84 | 0.0195 | 0.123 | 0.127 | OK

Next: About this document ... Up: class-weighting Previous: Consequences Contents