Solar Imaging Radio Array (SIRA)

1. Solar Imaging Radio Array (SIRA) R. MacDowall, N. Gopalswamy, M. L. Kaiser, M. J. Reiner Code 695 NASA Goddard Space Flight Center Greenbelt, MD 20771 USA sira.gsfc.nasa.gov

2. Overarching science question: what is the evolution of CME-driven shocks & CMEs from the Sun to 1 AU, and what are the resulting magnetospheric responses? • CME structure, propagation, & evolution, including topologies of interacting CMEs • Evolution of intermediate-scale solar wind structure and its effect on CMEs • Structure and dynamics of energetic electron beams from CME shocks & flares • Space weather prediction using radio imaging, including an exterior view of the meso-scale magnetospheric response to space weather • Mapping “astrophysical” sources, including coherent sources, steep-spectrum “fossil” radio galaxies, & serendipitous discoveries

3. Solar Radio Bursts – corona to 1 AU ? Note that radio imaging is complementary to coronagraphs, all-sky imagers, and scintillation observations.

4. scattering SIRA array Measurement improvement over state of the art: SIRA will provide the first high resolution imaging in the 0.1 to 10 MHz window

5. Roadmaps, history, schedule • Science Roadmaps: Understand the structure and dynamics of … the solar wind; understand the response of magnetospheres; predict … the evolution of solar disturbances as they propagate in the heliosphere and affect Earth (SEC Roadmap RFA’s 2003) • Previous MIDEX proposals (Astronomical Low Freq Array) • ALFA 1 (1995) – primarily astrophysics (JPL) • ALFA 2 (1998) – sub’d to both Astrophysics & Sun-Earth (JPL) • SIRA (2005) – first submission of Sun-Earth proposal by GSFC • Schedule: •Jan 2005 – Blue team Science review • April 2005 – Blue team Science Implementation review • Sep 2005 - Mission design/implementation complete • Focus on simplicity, reliability, and cost credibility

6. Overview of SIRA mission design • Orbital Sciences (OSC) recently selected as spacecraft provider with Partnership Opportunity Document (POD) • 12 – 16 microsats required for adequate # of baselines (microsat concept at right from OSC proposal; similar to GSFC IMDC design) • Lunar flyby provides rapid insertion into “retrograde” orbit at ~500,000 km (~80 RE) from Earth • Spring forced deployment provides initial Δv to put microsats on 10 km sphere • X-band direct-to-ground downlink from μsats • Science data centers at MIT and GSFC • “Pathfinder” for microsat constellations

7. SIRA technology issues • What are the top technical challenges? • deploying and operating a ~16 microsat cluster (note: OSC Orbcomm & ROCSAT heritage; THEMIS is a 5 s/c mission “breaking the ice”) • full-sky aperture synthesis imaging (note: ongoing work for wide-field ground-based arrays – Long Wavelength Array (LWA), etc.) • Is new technology needed? • Technology is at high TRL levels • Radio receivers: TRL 6 • Radio dipoles: TRL 9 • Carrier deployment mechanism: TRL 9 • Carrier flight software/components: TRL 5 • Cluster ops software/procedures: TRL 5 • Intersatellite ranging (3 m resolution): TRL 5, increasing to 6 by 2005, due to ST 9 & MMS LWA

8. SIRA microsat deployment SIRA heritage / partnerships • GSFC science team and partners bring strong heritage to space-based radio astronomy (ISEE-3, Voyager, Galileo, Ulysses, Wind, STEREO) • With OSC as a partner, we have all needed components for a low-frequency, space-based radio interferometry mission • GSFC internal partnerships: • systems engineering • proposal & project management • flight dynamics • ranging & other consultations SIRA science partners (and contributions): • Jet Propulsion Laboratory – aperture synthesis imaging • Mass. Institute of Technology – science data center • UC Berkeley – dipole antennas, solar wind, EPO • Catholic University – solar & IP radio astronomy • University of Iowa – planetary radio astronomy • Lockheed Martin – coronal radio astronomy, processing • Nat’l Radio Astronomy Obs. – IP medium, corona • Naval Research Laboratory – imaging; astrophysics • Observatoire de Paris-Meudon – radio receivers • Uppsala University – radio receivers, miniaturization • Swinburne University – aperture synthesis imaging

9. Summary SIRA is: • a mission central to NASA Sun Earth Connections and LWS goals & objectives, with important applications to the Exploration Initiative (space weather prediction) • the first high resolutionimager of solar radio emissions at < 15 MHz (0.01-1 AU) • built on GSFC, JPL, NRL, MIT, and UCBerkeley’s considerable expertise in solar, heliospheric, planetary, and astrophysical space-based radio astronomy; radio imaging is the logical next step • an ideal entry position for a significant microsatellite constellation (12-16 microsats) with simple spacecraft and instruments in a moderate radiation environment • a significant opportunity to conduct interferometry from space with applications to many future missions