Session
Technical Session V: Forecast for the Future
Abstract
The ongoing THEMIS (Time History of Events and Macroscale Interactions During Substorms) NASA mission is designed to understand the onset and macroscale evolution of magnetospheric substorms. A substorm is an instability in the circulation of magnetic flux and plasma through the solar wind magnetospheric system ultimately linked to the familiar auroral eruptions on Earth’s polar ionosphere. THEMIS’ five identical satellites will perform in situ measurements of particles and fields using a carefully choreographed orbital formation. The THEMIS mission consists of five identical small satellites manifested for launch on a Delta II 7925-10 from CCAS in October 2006. A number of interface lessons learned can be drawn from the completed design phase and the ongoing bus and instrument integration and test that are relevant to future SmallSat missions. This paper will examine in detail major system interfaces and explore the level of standardization applied, the pros and cons of the design choices made, with key observations highlighted below: • Sometimes it pay’s to pay up front –A flight proven transponder with industry standard interfaces was selected. The higher cost balanced with firm definition and proved to be the simplest and fastest to accommodate and finalize upon. • Some things can’t be standardized – Instrument thermal interfaces can be specified and captured in an ICD but only standardized comprehensive modeling will prove the interface validity. • The old adage; Keep It Simple Stupid (KISS) still holds true - Instrument power and communications interfaces were standardized to a single point between the instrument suite and bus then distributed on the instrument side of the interface to the multiple science sensors. This decoupled the bus from instrument sensor suite development and worked quite well. • In the end it’s the science that drives you – Evolving requirements is the challenge and the destiny of all science missions. It’s just not possible for cutting edge science missions that are competed to completely and comprehensively define all requirements up front. Nailing the interfaces down and identifying and communicating mission drivers within short schedules is key to success during the design.
Presentation Slides
SmallSat Lessons Learned on THEMIS: Approaches to Standard Interfaces that Succeeded or Failed
The ongoing THEMIS (Time History of Events and Macroscale Interactions During Substorms) NASA mission is designed to understand the onset and macroscale evolution of magnetospheric substorms. A substorm is an instability in the circulation of magnetic flux and plasma through the solar wind magnetospheric system ultimately linked to the familiar auroral eruptions on Earth’s polar ionosphere. THEMIS’ five identical satellites will perform in situ measurements of particles and fields using a carefully choreographed orbital formation. The THEMIS mission consists of five identical small satellites manifested for launch on a Delta II 7925-10 from CCAS in October 2006. A number of interface lessons learned can be drawn from the completed design phase and the ongoing bus and instrument integration and test that are relevant to future SmallSat missions. This paper will examine in detail major system interfaces and explore the level of standardization applied, the pros and cons of the design choices made, with key observations highlighted below: • Sometimes it pay’s to pay up front –A flight proven transponder with industry standard interfaces was selected. The higher cost balanced with firm definition and proved to be the simplest and fastest to accommodate and finalize upon. • Some things can’t be standardized – Instrument thermal interfaces can be specified and captured in an ICD but only standardized comprehensive modeling will prove the interface validity. • The old adage; Keep It Simple Stupid (KISS) still holds true - Instrument power and communications interfaces were standardized to a single point between the instrument suite and bus then distributed on the instrument side of the interface to the multiple science sensors. This decoupled the bus from instrument sensor suite development and worked quite well. • In the end it’s the science that drives you – Evolving requirements is the challenge and the destiny of all science missions. It’s just not possible for cutting edge science missions that are competed to completely and comprehensively define all requirements up front. Nailing the interfaces down and identifying and communicating mission drivers within short schedules is key to success during the design.
