Overview

Hisaki (SPRINT-A) was developed by the Institute of Space and Astronautical Science (ISAS) / Japan Aerospace Exploration Agency (JAXA) to observe planets in the solar system and their surrounding environments, especially to understand the dynamics of their atmospheres and magnetospheres. The main targets are planets such as Jupiter, Mars, and Venus, and the mission will observe the atmospheres and magnetospheres of these planets in detail.
The satellite was launched by an Epsilon launch vehicle from the Uchinoura Space Center on September 14, 2013, and completed its mission as a space telescope dedicated to planetary observations on December 8, 2023.

The satellite measures 1 × 1 × 4 m and weighs about 350 kg. It orbited at an altitude of 950 km perigee and 1150 km apogee in an elliptical orbit with a 34-degree inclination at a speed of about 106 minutes per revolution.

Observation Instruments

The scientific instrument onboard Hisaki is an Extreme Ultraviolet (EUV) imaging spectrometer.
A field-of-view (FOV) guiding camera was installed to stabilize the attitude variation within ±5 seconds.

Extreme Ultraviolet (EUV) imaging spectrometer

The EUV imaging spectrometer spectroscopically observes extreme ultraviolet radiation emitted from planetary atmospheres and magnetospheres to analyze the physical properties of these environments. Consisting of an incident mirror, three types of slits, two types of filters, a toroidal grating, and an MCP detector, the spectrometer resolves the 60-145 nm wavelength range into wavelengths with up to 0.4 nm resolution. From the wavelength and direction of arrival data of the detected photons in the extreme ultraviolet region, a two-dimensional spectral image in wavelength-space can be generated.

Field-of-view (FOV) guiding camera

The FOV guiding camera detects the image entering the slit of the spectrograph as a two-dimensional image. It can be used to determine the disk center of gravity of a target object.

Achievements

Hisaki’s observation data has provided a variety of new insights into the mechanisms of aurora formation in Jupiter’s magnetosphere and escape phenomena in Venus’s atmosphere. In particular, we now have a better understanding of the dynamics of plasma in Jupiter’s magnetosphere and its interaction with the solar wind. These results make important contributions to planetary science and space weather forecasting.