NSA/AERI/C1 - Excessive Noise in C1 AERI data
Initially it was believed that the greater noise level in AERI C1 data was due to the extended range detector, which has lower sensitivity. However, when the S01 AERI was installed next to the C1 AERI and it stabilized on 9/30/2005, it was observed that the noise levels on the newly installed S01 AERI were much lower than for the C1 AERI. Therefore, the excessive noise of the C1 AERI is not due to the fundamental nature of the extended range detector but instead due to failure within the detector. The failure could be due to a poor D* value of too high a detector temperature. It could also be caused by optical alignment issues. In either case, the spectral radiance data have much more noise and that results in larger error bars when using the radiance data, especially long wave data as monitored by the LW_HBB_NEN flag. On 9/30/2005, the S01 AERI, which is next to the C1 AERI, came on-line and is producing low noise data. The S01 data should be used instead of the C1 data where low noise requirements are needed. On 6/26/2006, the S01 AERI went offline due to a laser failure. The C1 AERI was moved to the connex where data were within reasonable limits for an extended range detector. Beginning 20060701, the C1 data are the preferred AERI data set at the NSA Barrow location.
Use S01 AERI as preferred data set 20050930-20060626. Use C1 AERI data as preferred data set after 20060701.