Small Satellite Conference - GEMS Presentation August 12, 2009

Big Astrophysics inA Small Package

Erin WalterGEMS Spacecraft Lead/Orbital

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?

• 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

Small Satellite Conference - GEMS Presentation August 12, 2009

GEMS Mission Overview

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-ClassLaunch Vehicle

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

Small Satellite Conference - GEMS Presentation August 12, 2009

Mission Operations