, (1)Calibration factors of AVNIR and OCTS level 1b data
M.Shimada/EORC/NASDA
1. AVNIR
Conversion of the AVNIR level 1b data to radiance is performed by the following way. Let the radiance and its corresponding digital number in level 1b product be Lt and DNC respectively, we have the following expression.
, (1)
where e
is the slope (and f is the offset (normally zero) (Table I). The recalibration of the radiance can be performed by using several reference signal sources.
, (2)
where
is the recalibrated radiance, g is the slope, and h is the offset. We call g and h the re-calibration factors [1].
MR : Mean Residual (W/m
2/sr/_m)2. OCTS
As same as for AVNIR, radiance of OCTS data in level 1b product can be calibrated by using the following equation. The calibration signal sources are two; AVIRIS under flight of the OCTS over the uniform ocean, and vicarious calibration data. The recalibration factor is summarized in Table II[2].
, (3)
Table II Calibration factor (g)
|
Band |
Calibration factor (AVIRIS) |
Vicarious calibration (I) |
Vicarious calibration (II) |
|
1 |
0.97 |
1.11 |
1.14 |
|
2 |
0.95 |
1.008 |
1.03 |
|
3 |
0.96 |
0.945 |
0.939 |
|
4 |
1.04 |
1.008 |
1.00 |
|
5 |
1.07 |
1.037 |
1.04 |
|
6 |
1.01 |
0.928 |
1.00 |
|
7 |
1.05 |
0.905 |
1.02 |
|
8 |
0.95 |
0.765 |
0.89 |
Note that the calibration factor is defined as the OCTS to AVIRIS radiance ratio.
[1] M. Shimada, H. Oaku, H. Oguma, R. Green, Y. Miyachi, and H. Shimoda
," Calibration of Advanced Visible and Near Infrared Radiometer", IEEE Trans. of Geosci. and Remote Sensing, Vol. 37, no. 3, may 1999, pp. 1472-1483.M. Shimada, H. Oaku, Y. Mitomi, Hi. Murakami,
and H. Kawamura," Calibration of the Ocean Color and Temperature Scanner," IEEE Trans. of Geosci. and Remote Sensing, Vol. 37, no.3, May 1999, pp. 1484-1495.