Epsilon/SPRINT-A Special Site

Messages from Project Managers

SPRINT-A to Elucidate Atmosphere and Magnetism of Planets with New Satellite Bus

By SPRINT-A Project Manager Shujiro Sawai

 At the outset of this project, I conducted a survey with my fellow space science professors and teachers about their idea of the configuration and performance of an artificial satellite as well as its orbit. The requirements are varied according to their research themes, and, if we aim at achieving the world's best research results, high-level performance and accuracy are a prerequisite.

After trying to meet as many future schemes as possible, the "SPRINT bus" was born. A bus is a core body of an artificial satellite that is equipped with basic functions such as satellite control and operation. It is like a tractor when you think of a large container trailer.

The SPRINT-A covers three orbits namely low-earth, elliptical and sun-synchronous orbits. The thermal designs for each orbit are different. The requirements for the center of gravity and the necessary power are also varied if we load a telescope or a magnetic sensor. When required power is different, the number of necessary solar array panels differs. The satellite attitude also has to be flexible to cope with requests such as to stabilize it at one precise position by three-axis control, and to spin it round by spin control. The bus that can meet various needs was completed after earnest discussions on every aspect even about a small tapped hole for a screw on a panel to attach a module.

JAXA called this bus the "SPRINT bus," which holds all necessary functions in a one-meter cube. The same technology is adopted for the "Advanced Satellite with New system Architecture for Observation (ANSARO)" developed by Japan Space System. This bus can be a basis of a semi-order satellite, and the first satellite based on the "SPRINT bus" is the Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere (SPRINT-A, or SPRINT-A/EXCEED at the time of development.)

The SPRINT-A will target Venus, Mars, Jupiter and their satellites by a telescope that can capture the extreme ultra violate region which cannot be observed from the ground. It will acquire scattered light from atmospheric ion hanging around the interplanetary space at Venus, and observe the Jupiter aurora caused by solar winds at Jupiter, and study the atmosphere and magnetism of planets.

For scientific artificial satellites, we used to be required to try to maximize each mission by applying specially ordered components and exclusive parts within just barely satisfactory limitations and restrictions. However, as the launch vehicle performance increased, and many electronics devices are getting smaller and lighter, payloads are allowed to be heavier by using common or commercial components. Consequently, we can launch a series of satellites and that helps us to increase our cost performance. This concept is shared by the Epsilon launch vehicle.

I have been involved in this project as an engineer; therefore, I sincerely hope that not only the SPRINT-A, but also many following artificial satellites with the "SPRINT bus" will go to space to open the frontier of new space science.

(Based on an interview)

Reprinted from JAXA's 048 (Seasonal magazine) dated January 1, 2013