Onboard Ranging System among multiple spacecraft for JAXA’s Formation Flight Mission

Paper number

IAC-08.B2.3.8

Author

Dr. Tomoaki Toda, Japan Aerospace Exploration Agency (JAXA), Japan

Coauthor

Dr. Yoshifumi Saito, Japan Aerospace Exploration Agency (JAXA), Japan

Coauthor

Dr. Yuichi Tsuda, Japan Aerospace Exploration Agency (JAXA), Japan

Coauthor

Prof. Kiyoshi Maezawa, Japan

Coauthor

Dr. Iku Shinohara, Japan

Year

2008

Abstract

Our next mission exploring magnetospheric region needs an onboard inter-spacecraft link system working for both data link and measurement support. We have reported our design and development of BBM (breadboard model) of this link system [1]. Another important aspect covered by our link system is to support acrobatic navigation of multiple spacecraft. Because ranging between spacecraft and ground station alone is not sufficient for a precise formation geometry determination, especially when spacecraft fly close to each other, inter-satellite ranging function is important. Ranging among spacecraft is also indispensable to keep universal timing for events in formation. We will discuss our inter-spacecraft ranging system employed in our next formation-flying mission.
  The mission to apply our link system is SCOPE (cross Scale COupling in the Plasma universE). It is designed as 4 or 5 spacecraft flying in formation and works in cooperation with another mission proposed by European science community. The inter-spacecraft link system of SCOPE is TDM/TDMA scheme sharing one S-band channel with one spacecraft as mother centered in the formation. We call forward link as one from mother to daughters and return link vice versa. The system assures fixed rate of 16kbps forward data link and maximum return link data rate of at most 500kbps. The ranging system was developed so as to co-exist with this data link.
  The requirement for inter-spacecraft ranging in SCOPE is satisfied with continual output of ranging result for every branch of the formation link with accuracy of one thousandth of the spacecraft varying distance from 1km to over 100km. Our system adopts two types of ranging to fulfill this requirement. Since our system has a mother-centered star network, the direct ranging is conducted by using forward and return link between mother and daughters. For ranging of branch distances among daughters, one slot in TDM/TDMA sequence is allocated for this purpose. The daughters exchange their clock timing information synchronized with mother master clock instead of establishing two-way link for each branch. This simplification greatly reduce difficulties of system modification when to increase and decrease the number of spacecraft in formation
  We have implemented this ranging system in our inter-spacecraft link BBM to confirm its function in TDM/TDMA scheme and evaluate its achievable precision and operation under realistic conditions including antenna switching.
[1] T.Toda, et al., ”Communication System Design for Formation Flight Magnetotail Research Mission: SCOPE”, 56th International Astronautical Congress, IAC-05-B3.6.06, Fukuoka, Japan, Oct. 2005.

Abstract document

IAC-08.B2.3.8.pdf

Manuscript document

IAC-08.B2.3.8.pdf (🔒 authorized access only).

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