Objective  Mars mineralogical spectrometer (MMS) is one of the scientific instruments for China's first Mars exploration mission. It is installed in the Mars exploration orbiter and performs spectral remote sensing detection of targets on the surface of Mars while in motion. The instrument has made breakthroughs in key technologies such as infrared background suppression, high efficiency spectroscopic structure, and on-device combined calibration. The characteristics of the instrument are light and small, low power consumption and high performance. The 512 pixel × 320 pixel short wave infrared (SWIR) integrated detector Dewar cooler assembly (IDDCA) is an important part of the MMS and is used for hyperspectral imaging. This paper analyzes the characteristics of the IDDCA in MMS, focuses on the development and technical difficulties of the infrared focal plane detector, integrated Dewar and integral rotary cooler, and also proposes approaches and methods to solve the technical problems.

  Methods  The 512 pixel × 320 pixel SWIR focal plane arrays (FPAs) is made of mercury cadmium telluride epitaxial material, prepared by n-on-p planar junction technology, is integrated CTIA input readout circuit, using indium column flip chip welding interconnection to form an infrared focal plane device. The detection signal of the 512 pixel × 320 pixel IR FPA is integrated, stored, converted, and outputted by using the window mode. The FPA architecture provides temporal detection in the SWIR bands using the frame integration incorporated into the readout integrated circuit (ROIC). The mechanical support of the integrated Dewar cold platform is a high-strength single cantilever cold finger, and a radial impact-resistant oblique support structure design is adopted (Fig.2). For the infrared Dewar in the MMS, the following designs have been applied: 1) Lightweight and impact-resistant integrated package structure; 2) Spectroscopic spectrum inside the assembly; 3) Special-shaped cold platform. The miniaturized integral Stirling cooler is selected, and the cooler drive control board is designed with an independent thick-film circuit required by aerospace.

  Results and Discussions   The overall technical requirements of the IDDCA for the MMS are shown (Tab.1). The results of the detector show that the signal to noise ratio (SNR) is 225 in the typical band of 1.595 μm. The thermal noise generated during the 40 ms long integration time of the detector is effectively eliminated by the integrated optimized cold platform (Fig.6). Moreover, the Dewar assembly is structurally sound after being subjected to random vibration of 14 grms (20-2000 Hz) and mechanical shock of 1400 g. The results of different fill pressure and cool down time of the cooler are shown (Fig.9). The actual installed product has the fill pressure of 42 mbar, which can ensure a long enough life from leakage to failure. Through the development of the above-mentioned key components, a good performance IDDCA was successfully obtained, and its main performance parameters are shown (Tab.6). The spectral test curve of the IDDCA for the MMS and the good infrared imaging effect in the spectrometer are shown (Fig.10).

  Conclusion  The IDDCA has advantages in aerospace applications of deep space exploration and interplanetary exploration due to their compact structure, low size, weight and power (SWaP). The application of this component for spaceflight is of great significance. This paper focuses on the design and implementation of key technologies such as high sensitivity, high signal to noise ratio FPA, anti-noise Dewar structure with long integration times, integrated long-life integral cooler. A series of mechanical and thermal environmental tests have been completed for the IDDCA. It was successfully launched with Tianwen-1 and reached Mars orbit, providing a certain reference for China subsequent deep space infrared spectroscopy detection.