1. Small Satellite Conference - GEMS Presentation August 12, 2009 Big Astrophysics in A Small Package Erin Walter GEMS Spacecraft Lead/Orbital

2. Small Satellite Conference - GEMS Presentation August 12, 2009 GEMS Mission The GEMS mission was selected by NASA as a Small Explorers (SMEX) mission in July 2009 and is scheduled for launch in 2014 on a Pegasus-class launch vehicle The GEMS mission will be the first mission to use x- ray polarimetry to characterize the geometry and behavior of x-ray sources, including supermassive black holes and magnetars. Answers to important questions – How does the spin of a black hole warp space time? – What powers magnetars? – How are cosmic rays accelerated in supernova remnants?

3. Polarization measurements allow us to study: Scattering Magnetic fields Strong gravity GEMS will use these processes to probe black holes, neutron stars and supernova remnants X-Ray Polarization

4. Small Satellite Conference - GEMS Presentation August 12, 2009 GEMS Mission Overview

5. Small Satellite Conference - GEMS Presentation August 12, 2009 Spacecraft Design Omni Antenna (1 of 2) Instrument Mount Points Rotating Entire Vehicle at 0.1 RPM Instrument interface: 3-point mount brackets on top deck Spacecraft bus provides: – 16 Gbits of data storage – 106 W of power provided – 4 RS-422 data interfaces – ACS Control and Knowledge – Ample throughput with RAD 750 processor – Fuses and power switches (including for instrument cover and boom actuation) Instrument is thermally isolated Instrument has no FOV impingements 2 Omni antennas mounted on instrument support structure for FOV optimization Pegasus- Class Launch Vehicle

6. Small Satellite Conference - GEMS Presentation August 12, 2009 Payload Design 0.1 rpm Rotation reduces systematic errors Three Telescopes – High signal to noise – Redundancy Three Mirrors – Light weight aluminum foil optics – Proven heritage from ASCA and Suzaku – Technology pioneered at GSFC – 4.5m focal length from extendable optical bench Three Time Projection Chambers Polarimeters – Photoelectric effect sensitive to polarization – Technology pioneered at GSFC ATK Boom Student collaboration Bragg Reflection Polarimeter

7. Small Satellite Conference - GEMS Presentation August 12, 2009 Mission Operations