DMSP

The Defense Meteorological Satellite Program (DMSP) satellites are polar orbiting satellites. DMSP has two sensors: the Operational Linescan System (OLS) and the Special Sensor for Microwave Imagery (SSM/I) data. The following sections describe the navigation and calibration blocks for each sensor.

DMSP navigation block

The table below lists the contents of the DMSP navigation block. The block contains 128 words and is used for all DMSP signal types.

Word	Value	Description
1	DMSP	navigation type; indicates the signal type being navigated
2		sensor source, year and date of the signal, ssyyddd
3		nominal time of image, hhmmss
4	1	orbit type; set to one
5		epoch date from the ASCII record below, yyddd
6		epoch time from the ASCII record below; days*1.e9
7		mean motion from the ASCII record below; deriv*1.e9
8		mean motion from ASCII record below; accel and mantissa
9		mean motion from the ASCII record below; accel and expon
10		bstart and mantissa; usually not used
11		b-start and expon; usually not used
12		inclination from the ASCII record below
13		right ascension of ascending node from the ASCII record below; deg*1.e6
14		eccentricity from the ASCII record below; ecc*1.e6
15		argument of perigee from the ASCII record below; per,deg*1e7
16		mean anomaly from the ASCII record below; anomalydeg 1.e6
17		mean motion; revs/day*1.e7
18-44		unused
45		data type; OLS, MT, MT2 or MI
46		ascending LT; 0=morning, 1=evening
47		number of first scan to navigate
48		time of first scan; sec*1.e3
49		scan flipped flag; 0=no 1=yes
50		element flipped flag; 0=no 1=yes
51		unused
52		number of elements per scan
53-120		unused
121-128		32-character ASCII record

The DMSP navigation block includes a 0-based, type 8 ASCII record, in words 120-127, that contains the scaled integer values used by the navigation block. The table below describes the ASCII record.

Character numbers	Description
3-4	spacecraft ID
6-17	epoch date; a decimal point indicates a fraction of a day
18-25	mean motion derivative
26-28	mean motion acc mantissa
28-30	mean motion acc exponent
32-39	inclination
41-48	RA of ascending mode
50-56	eccentricity
58-65	perigee
67-74	mean anomaly
76-85	mean motion

DMSP calibration

The OLS and microwave sensors use different calibration. The OLS calibration uses only one pair of of gain and offset parameters to transform infrared pixel values to radiance. The offset is set to 190.0 and the gain is set to .4706. The calibration module kbxols.dlm contains the offset pair. The visible pixels are not calibrated.

For the microwave sensors, each data line is calibrated and the information is stored in the documentation section. A postprocessor, DMSPCAL, calculates the gains and offsets from the information in the documentation section. The table below describes the calibration documentation for each line of data.

Bytes	Description
0-1	validity code
2-4	hot load temperatures; two measurements in byte 2, one measurement in byte 3
5-6	radiometer temperatures; forward radiometer temperature
7-13	instantaneous gain; one for each channel; these are calculated from the hot load temperatures and cold counts hotloadavg = average of 3 hotload temperatures hotcountavg = average of band hot counts coldcountbandavg = avg of band cold counts instantaneousbandgain = (hotloadavg-2.7k)/(hotcountbandavg-coldbandavg)
14-15	reference voltages; reference voltage and reference return both from block 6
16-20	cold voltages band 1
21-25	hot voltage band 1
26-30	cold voltages band 2
31-35	hot voltages band 2
36-40	cold voltages band 3
41-45	hot voltages band 3
46-50	cold voltages band 4
51-55	hot voltages band 4
56-60	cold voltages band 5
61-65	hot voltages band 5
66-70	cold voltages band 6
71-75	hot voltages band 6
76-80	cold voltages band 7
81-85	hot voltages band 7

When DMSPCAL is run, a gain and offset for each channel is placed in the calibration section of each scan line prefix. The table below describes the byte location of each gain and offset pair.

Bytes	Description
0-1	gain, band 1
2-3	offset, band 1
4-5	gain, band 2
6-7	offset, band 2
8-9	gain, band 3
10-11	offset, band 3
12-13	gain, band 4
14-15	offset, band 4
16-17	gain, band 5
18-19	offset, band 6
20-21	offset, band 6
22-23	gain, band 7
24-25	offset, band 7

[Search Manual] [Table of Contents] [Go to Previous] [Go to Next]