GISdevelopment.net ---> AARS ---> ACRS 1990 ---> Poster Session

Atmosphere temperature profile sounder, ATPS-II

Wang Mochan, Zhang ZhaoXiam
Shanghai Institute of Technical Physics,
Academia, Shangai, China


Abstract
There are twenty optical channels to detect vertical profile of Earth atmosphere's temperature in Atmosphere Temperature Profile Sounder (ATPS-II) and there is great breakthrough in infrared detector, narrow photo-filter, radioactive cooler and scanning step mirror control. Properties of optical mechanical and electronic system satisfied the requirement of design. Because of the great improvement of optical mechanism design ATPS-II has extensional abilities in long wave, short wave and visible channels. It extends the sound property of F-Y metrological satellites.

Introduction
The Atmosphere Temperature Profile Sounder (ATPS-II) in meteorological satellite has twenty optical channels to detect vertical profile of earth's atmosphere. It can provide the temperature, moisture and other meteorological factors of atmosphere profile timely and continuously, Especially in deserts, polar areas and oceans, which occupy 75% of Earth's surface. There is great significance for meteorological forecast of digital and middle long range.

Properties of ATPS_II are given in the blow:
Satellite Orbit
Satellite Orbit declination
Optical field of view (FOV)
Cross-track scan (CTS)
Number of step
Ground area of CTS
Ground Instantaneous field of view (IFOV)
Step time
Scan time
NEDN See Table 1
Calibration Stable Blackbody

Cooling space
Calibration period
Number of LW channels
LW detector
Number of SW channels
SW detector
Word length
Bit rate
Optical aperture
Weight about
Power
Size		 900km
98 degree
1.25 degree
+()- 49.5 degree
56
2240km
19.6km(nadir)
100ms
6.4s
See Table 1
290k
265k
3k
256s
12(See Table)
HgCdTe(6.7-15mm)
7 (See Table 1)
InSb (3.7-4.6um)
13 bit
2880 bits/s
150 mm
about 40kg
35w (average)
700*320320 mm3

Optical and Mechanical System
  1. Optical System

    Optical system is composed of scanning step mirror, D.K system relay and light cone hyperbolical concentrator (LCHC). LW, SW and visible channels in PTPS-II are used only one stop of view. So the identity of twenty optical channels IFOV is satisfied. From experiments, full IFOV of LW, SW and visible spectrum are equalized. It can give chances to extend the vision channel.

    LW photo-filters (120 and SW photo-filter (7) are installed in filter wheel which rotates in a period of 100 ms. Information of 19 channels are sequencely detected by IR detector. Due to the small dispersion. Fov's uniformity and small FOV lose. The LCHC is used.

    Major optical parments of ATPS-II are:
    Optical apeature
    Fnumber of main optices system
    System stop of main optices
    Full FOV
    Effective F number of system


    Stop of FOV
    Focus of area Longwave
    Shortwave
    Vision
    		 150mm (diameter)
    1.6
    0.21*0.15mm
    1.30 degree (LW)
    0.6417(LW)
    0.6732 (SW)
    0.9167 (Vision)
    5.40mm (diameter)
    1.92 mm (diameter)
    1.98 mm (diameter)
    2.50mm (diameter)

  2. Mechanical System

    Mechanical system is composed of calibrative blackbody's, main optics relay mechanism, scanning step mirror system, filter wheel, chopper, electronic box and base plate. The rotative components such as chopper and filter wheel require precise tempreture control for ATPS-II this was based on radiative energy exchange between two rotate components and uniform temperature shield (UTS.) the inner side of filter wheel and chopper are spread on black-paint in order to enhance energy exchange to UTS. The chopper and filter wheel are heatless connected with rotate axes. The accuracy of temperature will be less than 0.05k. Magnetic positional detectors are installed among the scanning step mirror, chopper and filter wheel for synchromotion control.
Infrared detectors, photo-filters and radiative cooler
LW has twelve photo channels (6.7-15mm). The detector is made by Gh Cd Te with area of 2.1*2,5mm2, D*p is 5 X 109 cm. Hz ½. W-1. The biased power is less than 15mw and working temperature is 105k.

SL has seven photo channels (3-5mm). The detector is made by InSb that D*P is superior to 5 X 1010 cm. Hz½. w-1 and working temperature is 105k also.

The visible spectrum detector is a silicium with fiel cone. Its sensational responsibility is 0.3 A/w and dark current is less than 3.X10-10 a with area of 3mm (diameter).

The narrow and super narrow interference photo-fiele (NIF) are key components in ATPS-II. Under the success study of nine narrow photo-filter in ATPS-I, Shanghai Institute of Technical Physics has manufactured twenty super narrow photo-filters to ATPS-II. TABLE 2 gives parameters of twenty super narrow photo-filters.

The radiative cooler in ATPS-II adhered to optical mechanism so that the structure is compact and improved the optical effectivenesss. The radiative cooler is experimented in cooler background of liquid nitrogen (80k) and liquid helium (29k). The second stage radiative cooler temperature is 111.3k and 98.6k.

Electronic System
Electronic system is composed fo Analog circuits of LW,SW and visible spectrum Multiswitch, A/D converter, Microprocessor I, Microprocessor II, Driver circuits of scanning step motor, chopper motor and filter wheel, temperature measurement and control circuits power of DC converter and so on.

Analog circuits are made from preamplifiers, clamp circuits, electronic filters. Phase amplifiers and integrators.

It is important to solve problems of the error from the interactive effect of electronic signals in different optical channels and the ratio of gignal-noise in analog circuits. According to experiments and theoretical calculates, the band with of analog circuits are 670 Hz to 1250 Hz (LW circuit), 420 Hz to 1500 Hz (SW circuit) and 170 Hz to 1750 Hz (visible).

Functions of Microprocessor I in ATPS -II are:
  • Data acquisition from 13 bites A/D converter then preprocessing it

  • Connected with F-Y Information processor (FIP)

  • Two pattern control of step scanning motor (fly pattern and calibration patttern)

  • The transitional processing control of step scanning motor in steps
The transitional processing control of step scanning motor is a key technique, which influence properties of ATPS-II. The transitional process of High Resolution Radiation Sounder (HIRS/2) in TIROS-N and NOAA satellites series (US) is controlled by use of close loop control of step motor, velocity motor and torque motor only have 35 ms in the transitional process. In ATPS-II. We use electronic control technique to control transition process of step scanning motor and the transitional time is less than 15ms. Compare to HIRS/2, two LW channels and one SW channel are added and extend the ability of TPS-II.

Microprocessor II consists of following functions:
  • Output diffent control signals that analog circuits, Multiswitch and A/D converter

  • Send out standad signals for electronic calibration.

  • control photo-filter wheel and chopper for synchromotion

Conclusion
There is a great breakthrough in IR detectrs, narro photof;iters, radiative cooler an transitional process control of scanning step. The optical, mechanical and electronic properties satisfied the requirement of design of ATPS-II . Because of the great impovement of opticalmechanism in ATPS-II, it extend the ability of LW, SW and visible channels and develop the functions of F-Y Meterological Satellites.

References
  1. E.W.K oening, NASA-CR-144743, 1975, 28670

  2. Arthur Schwalb, the TIROS-N/NOAA A-G Satellite Series, NESS 95, Wasthington D.C. Mar. 1978

  3. Wang Mochang, Atmosphere Temperature Profile Sounder, ATPS-1, Chinese J. In frared Res. 6(1987) 17-23.