1.

Introduction

Meteorological satellites have become an irreplaceable weather and ocean observing tool, while the infrared detection has become a key technology in the development of meteorologicalsatellites. Because the wind and cloud are the main objects to be observed by the meteorological satellites to explore the weather, the meteorological satellites in China has been named as Feng-Yun satellites. The pronunciation of “Feng” and “Yun” corresponds the Chinese words “wind” and “cloud”, respectively.Up to now, the main observation is on the cloud for the meteorological satellites, and the observation technology to observe the wind is exploring. The infrared technology has been developed in Shanghai Institute of Technical Physics (SITP) to observe the cloud in the series of Feng-Yun in Chinese meteorological satellites more than 40 years. The infrared payload on the Feng-Yun series is mainly studied and finished in SITP. Since the first Chinese polar-orbiting meteorological satellite Feng-Yun (FY-1A) was launched in 1988, there are more than 10 meteorological satellites being launched into both sun synchronous and geostationary orbit as listed in table 1.And more satellites are developing as the second generation ones where the infrared payload will play a key role to observe the cloud distribution and evaluation.

Table 1

Chinese meteorological satellite

2.

Infrared payloads in meteorological satellite

Infrared remote sensors are the main payloads on-board each meteorological satellite. As the unique remote sensor on-board the first generation polarorbitingmeteorological satellites (FY-1 series) and the geostationary orbit meteorological satellites (FY-2 series) separately, 10-channel Visible and InfraredScanningRadiometer (VIRSR) and Visible and Infrared Spin-Scan Radiometer(VISSR) had been developed since 1970s’. The long-term operational ones have been working for over 10 years, and obtain the remote sensing data for oceancolour, water vapour, weather forecasting, etc. The two types of meteorological satellites The main infrared payloads developed in SITP is listed in table 2 and 3 for both the first generation and second generation of meteorological satellites.

Table 2

Infrared payloads onboard polar-orbit satellites

Table 3

Infrared payloads onboard geostationary satellites

There are four type of infrared sensors which are carried aboard each platform of the second generation polarorbitingmeteorological satellite (FY-3): the Visible and InfraredRadiometer (VIRR), MediumResolution Spectral Imager(MERSI),Infrared AtmosphericSounder (IRAS),Earth Radiation Measurer (ERM). As the results of the three launches of FY-3A, FY-3B and FY-3Csatellites, three groups of these four sensors are currently operating on-orbit andproviding not only the imaging data, but also the sounding data and Earth radiance budget data at the same time. MERSI surveys the earth with a ground pixel resolutionof250-metre and a swath width over 2900 km, thatcould get the global TIR image of 250-meter resolution twice each 24 hours. This specification is distinctive and useful for the environmental monitoring. The global image mosaic from MERSI of FY-3A is shown in Fig.1.As the upgrading sensors of MERSI and IRAS, MERSI-II and High-spectral Infrared Atmospheric Sounder (HIRAS), focusing on imaging and sounding mission separately, are developed and will be launched with FY-3D. They will get more infrared channels and fine spectral data in the near future.

Figure 1.

The global image mosaic from MERSI of FY-3A observed in 19 July 2008.

Table 4.

Infrared payload comparison among FY-4, GOES-R and Himawari-9

Two type of infrared sensors, advanced geostationary radiometric imager (AGRI) with 14 channels and geostationary interfering infrared sounder (GIIRS), are constructed for the second generation of the geostationary-orbit meteorological satellite (FY-4). The AGRI can obtain the global image very 15 minute as shown in fig.2. The GIIRS can obtain the high resolution IR spectrum with the special resolution of 16Km to get the atmospheric temperature profile and humidity profile. The typical atmospheric temperature profile observed is shown in fig.3. The detail characteristic of AGRI and GIIRS is listed in table 3. Compared with other two newly launched meteorological GOES-R (@2016/11/19) and Himawari-9(@ 2016/11/2), the Radiometric Imager has the similar performance. As a progress, the FY-4 has integrated the both Radiometric Imager and interfering IR Sounder together to improve the data usability for atmospheric analysis.

Figure 2.

The image obtained by advanced geostationary radiometric imager on FY-4

Figure 3.

The 3 dimensional temperature profile obtained by geostationary interfering infrared sounder on FY-4

3.

Infrared detector for the payloads in meteorological satellite

Up to now, the main infrared detector used on the Feng-Yun meteorological satellite is HgCdTe photo-detector. The very long wavelength HgCdTe detector has been developed for the geostationary interfering infrared sounder on FY-4. It has the following characteristic: format: 32×4, cutoff wavelength: λc=15.3μm, Detectivity: 5.05×10¹⁰ cmHz^1/2/W, Responsivity: 1.42×10⁴ V/W, Non-uniformity: 5.47%, Crosstalk: 4%, and operation temperature: 65K.

In order to get the large format of long wavelength focal plan array for IR payload in meteorological satellite, two type of quantum infrared photo-detectors has also been developed. One is the type II super-lattice long wavelength IR photo-detector. It has the format of 320×256 with the average peak detectivity (@10.6μm) of 3.4×10¹⁰ cmHz^1/2 W^-1 at 65K. The second is the quantum well IR photo-detector. It has the format of 320×256 with the average peak (@15μm) detectivity of 1.4×10¹⁰ cmHz^1/2 W^-1 at 50K.

4.

Conclusion

The infrared payload technology has been developed in SITP, it has shown it high impact on the Chinese meteorological satellite. It will continue its important role in the roadmap of Chinese meteorological satellite. The high performance infrared detector will be the key technology for the infrared payload in the FY3 and FY-4 meteorological satellite to be launched in 2018, 2019, and 2020.