Instrument, Spacecraft, and Launch Overview

Joan Howard

Ball Aerospace

Instrument Requirements

Parameter Requirement FeaturesWaveband 95μm Matches Available

SIRTF FPA’sDetector AngularSubtense

48 seconds Oversamplingdiffraction blur

Field of View ~26 minutes Matches 32x32 currentdetectors

S/N Req: 150 Goal: 600Cooling Detectors<2K;

Optics<6KLight shade limitingcryo load on lastproposal

Instrumentpolarization

<1% Analysis meets

Calibration <1% source Use standard source

Ball Heritage• Currently building SIRTF CTA and instrument which

uses Ge:Ga FPA’s– Past CDR in subassembly test

– No major technical showstoppers

• IRAS flying successfully– very similar from a cryo design - only smaller

• Conceptually simple design– simple electronics, tested FPA’s, small/few element optics,

but….

– Cryo design never simple

Spacecraft Requirements

• Low Cost - less than $15M?

• Accept >125 kg instrument

• Provide > 30 Watts of power to payload

• Pointing Stability < 24 seconds per data acquistion

• Fit into selected Launch Vehicle

• Data Storage: 200 Mbytes

Spacecraft Key Performance Requirements

Description X-12M SMEX LITE SA-200SMiniStar

Spacecraft Bus Mass 65.6 kg 75kg 98kgPayload Mass Capability 200 kg 91kg 200kg

180kgAvailable Payload Power > 100 W 150W 60W 17.5WACS Configuration 3-axis stabilized 3 axis zero momentum

Gravity GradientAttitude Knowledge 28 μrad 5μrad

.5 degreesAttitude Control 32 μrad 96μrad 10 degreesPayload Data Storage 256 Mbytes 130 Mbytes 8Gbyte

3MbytesCommunications S-Band S-Band S-band S-bandTelemetry Rate 4Mbps 2.25Mbps 10Mbps 1 Mbps

Equipment Shelf Provides Ample Area For Subsystem Units

TRANSPONDER

TORQUE ROD

(3 PL)

INERTIAL

REFERENCE

UNIT

BATTERY

STAR TRACKER

REACTION WHEEL

(3 PL)

FLIGHT COMPUTER

RELAY BOX

S/C Selection• Meets minimum requirements

• Lowest total cost– nearly all COTS buses will need changes

– integration issues

– heritage of performance: technical, cost, schedule

• Willing to work with team

• Selection not mandatory for 1st round - a solution, not the solution needed

Issues/risks/options• Need good story for aperture cover - esp. after

WIRE

• Light shade a key driver in itself and for cryo design

• Star tracker vs. gyro

• battery size vs. eclipse

• CPU capabilities/memory - on orbit computation vs. downlink

• configuration drivers: LV, COTS, star tracker location, timeline, launch date

Launch Options

Option Pros ConsDedicated Launch We have more timing

control, fewer constraintson design, right orbit

$$$$$$$$$

Share with equal Workable timing, co-manifest layout, right orbit

How to find the partner,stay coordinated throughoutprogram

Rent a ride Save $$$$$ - maybe$15M, huge mass margin

No launch timing control,not many LEOopportunities, feweropportunities that wouldaccept cryo, orbit may beproblematic