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varenius / salsa

Code developed for the 2.3m radio telescopes SALSA in Onsala, Sweden
MIT License
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Move Trec (receiver temperature) to config file #63

Closed varenius closed 3 years ago

varenius commented 3 years ago

Vale and Brage can use approximate calibration from ambient temperature + Trec. Now hardcoded in https://github.com/varenius/salsa/blob/main/Control_program/main.py#L413 as 50 K. However, the two telescopes may be different. Brage has e.g. longer cable, so signal is less compared to noise. Therefore it could be nice to put Trec in SALSA.config instead.

varenius commented 3 years ago

Comparison on GLON 80, GLAT 0. Vale: vale-crop.pdf Brage: bragefit-crop.pdf Current outside temperature is 15 C = 288 K. Assumed Trec = 50 K so Tsys is 338K. We assume the peak should be 95K in the AllSky data. Processing the data quickly in matlab to fit baseline. Based on this single check, scaling factors to be applied would be Vale: 95/155 = 0.6 --> Tsys should be 202K. This is surprising, but perhaps possible if we're looking at the sky? The average temperature could be lower than ambient since the sky background is clod? Brage: 95/110 = 0.86 --> Tsys should be 287K so ambient temp. This is a bit surprising since I found the empirical Trec factor a few months ago. Well, it seems setting the Trec = 0 would be an even simpler fix. Trying that first...

varenius commented 3 years ago

Different direction, trec 0. GLON 80. Peak is now brage: 75K, vale: 55K. So quite big variation. This could potentially be pointing-model related, so further refinements should be done after a proper pointing model has been established. No reason applying individual Trecs until we know other factors which can impact. Hence closing this.