- 著者
-
Hiroshi ARAKI
Ko ISHIBASHI
Noriyuki NAMIKI
Hirotomo NODA
Masanori KOBAYASHI
Keigo ENYA
Masanobu OZAKI
Takahide MIZUNO
Yoshifumi SAITO
Kazuyuki TOUHARA
Shoko OSHIGAMI
Shingo KASHIMA
Jun KIMURA
Shingo KOBAYASHI
Gregor STEINBRUEGGE
Alexander STARK
Christian ALTHAUS
Simone Del TOGNO
Kay LINGENAUBER
Hauke HUSSMANN
- 出版者
- THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES
- 雑誌
- TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN (ISSN:18840485)
- 巻号頁・発行日
- vol.17, no.2, pp.150-154, 2019 (Released:2019-03-04)
- 参考文献数
- 10
- 被引用文献数
-
1
GALA (GAnymede Laser Altimeter) is one of the payload instruments of the JUICE (JUpiter ICy moons Explorer) project to be launched in 2022 to the Jovian icy moons Ganymede, Europa, and Callisto. GALA is developed through an international collaboration between Germany, Japan, Switzerland, and Spain. With the performance model of GALA, we have sought to create the interface conditions that satisfy the science requirements on the probability of false detection (PFD) and the range accuracy. The science requirements on GALA performance can be summarized as involving the following four criteria: [1] for Europa fly-by, PFD is less than 0.2 from an altitude of 1300 km or lower, [2] under the worst observation condition for albedo and surface slope of GCO500 (Ganymede Circular Orbit whose height is 500 km), the accuracy of ranging is less than 10 m and PFD is less than 0.2, [3] under the nominal observation condition of GCO500, the accuracy of ranging is less than 2 m and PFD is less than 0.1, and [4] under the best observation condition of GCO500, the accuracy of ranging is less than 1 m and PFD is less than 0.1. For the assessment, however, we had used literature data as the characteristics of the laser detector of GALA, avalanche photodiode (APD), which should be degraded due to the severe radiation environment around Jupiter. Then we carried out a more realistic model simulation of GALA by incorporating these degradation effects of APD. Characteristics of APD, such as gain, quantum efficiency, excess noise index, surface dark current, and bulk dark current, were re-evaluated through radiation tests using the data of dark and photo current of the APD irradiated with 2-MeV-electron and 50-MeV-proton beams, which are the radiation conditions assumed for JUICEGALA around Jupiter. These degraded characteristics of APD by radiation were introduced to our performance model of GALA. As a result, our performance simulation of GALA showed again that the science requirements are satisfied even after taking into account the degraded characteristics of APD. The remaining matter is the effect of noise or digitization in the Analog Electronics Module (AEM), which must be taken into account for the final specifications of GALA.