McIDAS Programmer's Manual

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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; anomaly*deg*
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

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