Welcome to ASF’s Quality Assurance Group. Here you will find information about the data calibration efforts we have completed, are working on now, and plan to begin in the future. You are encouraged to contact us if you have any questions or comments. We are here to serve you!

The Alaska Satellite Facility receives data from satellites orbiting in space. ASF takes the data from these satellites and creates images which are distributed to users of the data. These images are actually measurements of a physical parameter called "normalized RADAR cross section" or NRCS.

Let's discuss a different measurement for a minute. If we build a scale with a needle that moves, it's not much use to anybody yet. We need those little marks under the needle that show how much the object weighs. We can just choose some nice sounding numbers, like 0 kg, 50 kg, 100kg and write them on the scale. Our scale will probably not serve us well because the needle may point to the 50 kg mark when you put 1 g on it! So we have to calibrate the scale. The easiest way to do this is to take all the weight off of the scale. We then write "0 kg" where the needle is currently pointing. Then we put something we know to weigh 50 kg on the scale and write "50 kg" where the needle points with the weight on it. Finally, we can put a 100 kg mass on the scale and write "100 kg" where the needle is pointing. We now have a calibrated scale the - numbers that the needle point to have been adjusted so they are correct.

To calibrate any other measuring device, including a Radar processor, works pretty much the same way. We use the device to measure a known quantity, and adjust the device's output accordingly. We use standard masses for scales, standard lengths for rulers, and standard volumes for measuring cups. The images ASF distributes are measurements of NRCS, and we use Corner Reflectors and the Amazon Rainforest, which have known radiometric and impulse response values, to calibrate the measurements.