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operations:tsys
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operations:tsys [2011/03/02 04:11] Stas Shabala |
operations:tsys [2011/10/26 06:37] (current) |
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| ====== Y-Factor and Tsys Measurements ====== | ====== Y-Factor and Tsys Measurements ====== | ||
| - | System temperature includes a number of contributions: receiver, atmosphere, CMB, plus antenna effects such as groundspill, surface imperfections etc. It can be measured by comparing observations of the sky and of a known load, | + | ===== Calculation ===== |
| - | (T<sub>load</sub> + T<sub>LNA</sub>) / T<sub>sys</sub> = Y | + | A [[operations:tsys_method|description of the method used to calculate Tsys and Tcal]] |
| - | where the measured Y-factor is given in terms of the difference in measured power (in decibels), | + | ===== Results ===== |
| - | Y = 10<sup>0.1(P<sub>load</sub>-P<sub>sky</sub>)</sup> | + | A spreadsheet containing all data and calculations to date is in {{:operations:y-factors_2011_hb12_2011_march_08.xls|}} |
| - | Typical values are P<sub>load</sub>-P<sub>sky</sub> = 4.5 - 6 and hence Y = 2.8 - 4. | + | The following is a summary of the data so far |
| - | Hence T<sub>sys</sub> = (T<sub>load</sub> + T<sub>LNA</sub>) / Y | ||
| - | Load temperature is just the ambient temperature (in Kelvin), and the LNA temperature is assumed to be 45K. | + | ^ Tsys (K) ^^^^^^ |
| + | ^ Date ^ S-band ^^ X-band ^^^ | ||
| + | ^ ^ LCP ^ RCP ^ LCP ^ RCP ^ Note ^ | ||
| + | | 2010 Sep 06 | 87 | 95 | 84 | 81 | S-band filter at 2260 MHz | | ||
| + | | | 84 | 84 | | | S-band filter at 2300 MHz | | ||
| + | | | 80 | 90 | | | S-band filter at 2350 MHz | | ||
| + | | 2011 Feb 28 | 109.5 | 113.3 | 89.7 | 89.3 | S-band with narrow-band filters at 2250 MHz | | ||
| + | | 2011 Mar 03 | 109.6 | 111.6 | 85.6 | 85.1 | S-band with narrow-band filters at 2250 MHz | | ||
| + | | 2011 Mar 08 | 95.3 | 101.4 | 83.2 | 83.5 | as above | | ||
| - | With the system temperature known, there are two ways of calculating the noise diode (cal) temperature. When measurements of the sky and load are both made with the diode included, | + | ^ Tcal/Tcal,2 (K) ^^^^^^ |
| + | ^ Date ^ S-band ^^ X-band ^^^ | ||
| + | ^ ^ LCP ^ RCP ^ LCP ^ RCP ^ Note ^ | ||
| + | | 2010 Sep 06 | 3.0 | 3.7 | 6.2 | 6.7 | S-band: 2260 MHz | | ||
| + | | 2011 Feb 28 | 6.3/6.4 | 5.6/5.9 | 11.8/11.9 | 10.7/10.6 | S-band : 2260 MHz | | ||
| + | | 2011 Mar 03 | 6.5/6.7 | 6.5/6.1 | 17.2/16.7 | 15.7/15.3 | S-band : 2260 MHz | | ||
| - | T<sub>cal</sub> = (T<sub>load</sub> + T<sub>LNA</sub> - Y T<sub>sys</sub>) / (Y-1) | ||
| - | |||
| - | When the diode in included in the load measurement, but not in the sky-only measurement, | ||
| - | |||
| - | T<sub>cal,2</sub> = Y T<sub>sys</sub> - T<sub>load</sub> - T<sub>LNA</sub> | ||
| - | |||
| - | Measurements for Feb 28 on the Hobart 12m are given below. | ||
| - | |||
| - | {{:operations:hb12_tsys.xls|Hb12_Tsys.xls}} | ||
/home/www/auscope/opswiki/data/attic/operations/tsys.1299039080.txt.gz · Last modified: 2011/10/26 06:37 (external edit)
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