An overview of Solar Sentinels mission architecture selection

Paper number

IAC-08.A3.6.4

Author

Ms. Karen Kirby, Johns Hopkins University Applied Physics Lab, United States

Year

2008

Abstract

NASA’s Solar Sentinels mission is an inner heliospheric mission to investigate, characterize and understand how the Sun influences the environment of the inner solar system, and more broadly, how the heliosphere is formed.  The Sentinels mission is composed of four identically instrumented spinning spacecraft, flying in a constellation, which will observe the energetic particles environment, solar wind and coronal mass ejection structures in the inner heliosphere by operating in an elliptical solar orbit from 0.25 to 0.73 AU.

In February, 2008 engineers at the Johns Hopkins University Applied Physics Laboratory completed a study report for NASA detailing this unique Sentinels mission architecture.  The challenges were to make in situ observations from multiple platforms arrayed at varying radial distances and azimuth locations in a near ecliptic plane and to provide a spacecraft design to accommodate the thermal and power generation challenges for operation at close distances to the sun. The spacecraft design must protect spacecraft electronics and accommodate a suite of sensitive instruments while providing spacecraft communication to earth at a maximum distance of 1.7 AU earth distance.

This paper will describe the mission concept and spacecraft architecture and will discuss the trade studies that were completed to select the mission design. Solar array configurations were compared and contrasted for deployed versus body mounted fixed solar arrays. Trade studies were done comparing parabolic dish and phase array high gain antenna configurations.  Single string versus redundant spacecraft designs were considered, and three-axis stabilized versus sun-pointed and ecliptic spinning architectures were evaluated, all with the consideration to enable the launch of a set of four spacecraft with a single EELV launch vehicle. Configuration options were compared with the science goals and objectives in order to select the spacecraft configuration that provides the lowest cost, lowest implementation risk, simplest operation and the most benefit for the science implementation.

The selected mission architecture includes four identical 560 kg spacecraft stacked for launch on an Atlas V-421 launch vehicle, each providing 54 kg and 45 W allocated to the instrument suite. The spacecraft will be arrayed in the desired orbit configurations using Venus flybys and trajectory correction maneuvers and they will operate in a spin stabilized mode at a 20 rpm spin rate. Body mounted solar array panels and a single deck design with passive louver thermal control are selected as the optimum configuration to meet the demands of the thermal environment at 0.25 AU. The rationale for these design decisions will be discussed in detail and the conclusions will show why it is fitting that this mission is the next element of NASA’s Living with a Star program.

Abstract document

IAC-08.A3.6.4.pdf

Manuscript document

IAC-08.A3.6.4.pdf (🔒 authorized access only).

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