Magnetic Tapes NMRT

The preparation of digitized tapes has numerous obstacles to overcome. A CDC 924 computer is used for calibration then, combining the calibrated tape with the telemetric information, we obtain the definitive digitized tape (NMRT). This is a huge and costly job. Calibration itself is rarely correct as far as absolute values go, but is valuable if we are wise enough to consider only the reciprocal relationships, the gradients. 

Random noise can be temporary, as that caused on a TV set by a passing automobile with a defective antistatic system. Correction is simple. Noise can also be permanent, caused by an irreparable malfunction in the receiving set (in which case we pick up another one at the store) or in the transmitter. To come back to satellites, it goes without saying that such a fault, accidental though it may be, is there to stay. This is what happened on board Nimbus 2 through 5. On the other hand, when the cause of the trouble has been diagnosed, it can be remedied by the apparatus described below. 

For example, the oblique lines affecting Nimbus 1 photofacsimile came from periodic interference having a frequency of 16 Hz. This was corrected for later satellites, which are affected by medium frequency interference (200 Hz). In the latter case, errors reached and exceeded 3 K upon calibration, and increased considerably at low temperatures (Williamson, 1970). 

If interference ihtroduced during ground operations is (or could be) eliminated, it is not the case for interference originating on the satellite. In this case, digital filters are applied which attenuate to a degree the area occupied by undesirable signals. 

Contrast between successful injection into orbit and delays in using information 

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