Keywords: clic

Next: Receiver temperature Up: Atmosphere Previous: Atmosphere Contents Index

#### Measurements

Assume we have a system that measures the total power received at the output terminal and that input power is measured in temperature scale (see eq. 2) with an unknown gain ( ) i.e. we have:

| (44)

Similarly, let's assume that the autocorrelations are on a power scale with a gain , different from , but the same for auto- and cross- correlations (this point is checked with measurement on a noise source, which is fully correlated for different antennas, so that autocorrelations match the crosscorrelation amplitudes). Then we have:

| (45)

where is the source power at the input port.

In using the chopper wheel method, we place loads with known effective temperature in front of the receiver. For NOEMA, one uses a hot load made of absorber which is at the temperature of the receiver cabin and a cold load located inside the cryostat on the 15K stage ; regular observations are made on the sky:

|  |  | (46)
|  |  | (47)
|  |  | (48)
|  |  | (49)
|  |  | (50)

The difference between the cross-correlation amplitudes and the autocorrelations is that the "noise" (i.e. ) is uncorrelated between different antennas and vanishes from the cross-products.

Next: Receiver temperature Up: Atmosphere Previous: Atmosphere Contents Index