Building Canada’s Future In Space

ArcMinute ArcMinute Attitude Control: Enabling Attitude Control: Enabling Technology for the Bright Star Technology for the Bright Star

Photometry Photometry Nanosatellite Nanosatellite MissionMission

Robert E. ZeeManaging Director, Space Flight LaboratoryUniv. of Toronto Inst. for Aerospace Studies

Kieran A. CarrollManager, Space Projects

Dynacon Inc.

Slavek RucinskiAssociate Director, David Dunlap Observatory

University of Toronto

10 August 2004

Building Canada’s Future In Space

Overview

Betelgeuse from NASA/HST

• Examine bright, luminous stars through stellar photometry from space. Characterize stellar properties. Find non-variable stars to act as reference standards for other programs.

• Targets with long variability periods (hours to weeks).

• 10x greater accuracy from space.

• 3-cm aperture telescope and CMOS detector.

• Three-axis stabilized nanosatellite: CanX-3 (2-3 kilograms) aka BRight Target Explorer (BRITE).

• Leverages CanX student program and MOST ACS technology.

• Target launch late 2006, early 2007.

Building Canada’s Future In Space

BRITE Science• Evolution and internal structure of stars

by measuring brightness fluctuations.

• From burst phenomena to seismic variations.

• Complementary to MOST microsat mission.

• Study massive stars with short lives. Evolution leads to heavy elements and UV photons supporting the formation of organic matter.

• Extremely bright (100x Sun) allows use of small instrument.

• Must have stable observations over days, weeks, months.

• Ground-based campaigns limited by atmospheric extinction and bright star separation. Coverage also limited by day-night cycle.

Intrinsic Luminosity of Stars of Magnitude 3.5 and Brighter

Building Canada’s Future In Space

BRITE Instrument• Requirements

– Magnitude –1.5 to 3.5, 20 ppm– View a given direction for up to 6 months for variation

periods ranging from 2 hours to 2 weeks.– One observation (up to 15 min) per orbit for each of three

target fields.– Wide FOV (min 15°x15°) to capture multiple bright stars for

differential photometry.– LEO, 400-900 km. No other restrictions on orbit.

• Design– 3-cm aperture telescope, 25° FOV, CMOS imager.– Smear image over multiple pixels.– Sun or Earth angle > 90° to avoid excessive baffling.– Passive radiator, keep focal plane < 10°C (for dark current)

Building Canada’s Future In Space

ProgramCanadian Advanced NanoSpace eXperiment

• Graduate students build their own nanosatellite (< 10 kg) in 2 years.

• First satellite, CanX-1, launched on 30 June 2003. Completed in 22 months.– Imaging of Earth, Moon, stars using

CMOS Imagers

– Star/horizon tracking experiments

– Demonstration of GPS from space

– Magnetic attitude control

– ARM7 on-board computer (OBC)

– Triple Junction Cells, Li-ion battery

– Custom UHF Transceiver

Est. 2001

Building Canada’s Future In Space

Nanosatellite Launch System• UTIAS/SFL arranged launch for NLS-1

(containing CanX-1, DTUSat, AAUSat) and NLS-2 (containing QuakeSat) and provided integration, test, and launch support.

• CalPoly provided P-POD launch tubes and associated support.

• Liftoff 14:15 UTC 30 June 2003, Plesetsk, Russia – “Rockot” Launch Vehicle.

UTIAS Clean-Room

NLS-1 Mounted to Upper Stage of Rockot LV (modifiedSS-19 ICBM) atPlesetsk CosmodromeRussia

Building Canada’s Future In Space

CanX-2 Project Underway• Mission Objectives

– Evaluate new systems– Some scientific investigations planned

• GPS Radio Occultation (Calgary)• Materials Experiment (Toronto)• Atmospheric Spectrometry (York)• Nanotechnology (Toronto)• Novel Comm Software (Carleton)

– Increased Staff Involvement– Target late 2005 launch.

• Design– “Double CubeSat”

(10x10x20 cm)– 2 kilograms nominal

Building Canada’s Future In Space

CanX-2 Technology• Custom ARM Computers

• CMOS imagers on OBC

• UHF up and S-band down (32 kbps to 1 Mbps).

• Triple Junction Cells and Li-ion battery.

• High performance L1/L2 GPS receiver.

• Momentum bias ACS with Dynacon NanoWheel.

• Custom Sun Sensors (100° FOV, approx. 1° accuracy).

Main OBC Main OBC

Payload OBC Payload OBC

Spectrometer Spectrometer

GPS GPS

Momentum Wheel

Momentum Wheel

Surface Materials Surface

Materials Calorimeter Calorimeter Magneto - meter

Magneto - meter

Sun Sensor Sun

Sensor Sun Sensor Sun

Sensor Sun Sensor Sun

Sensor Sun Sensor Sun

Sensor

Power System Power System

Test Port Test Port

Deployables Deployables

Beacon Beacon UHF Radio UHF Radio

S - band Transmitter

S - band Transmitter

Magnetorquer Magnetorquer Magnetorquer Magnetorquer Magnetorquer Magnetorquer

Async . Serial SPI Power Discrete I/O HDLC

Legend

Main OBC Main OBC

Payload OBC Payload OBC

Spectrometer Spectrometer

GPS GPS

Momentum Wheel

Momentum Wheel

Surface Materials Surface

Materials Calorimeter Calorimeter Magneto - meter

Magneto - meter

Sun Sensor Sun

Sensor Sun Sensor Sun

Sensor Sun Sensor Sun

Sensor Sun Sensor Sun

Sensor

Power System Power System

Test Port Test Port

Deployables Deployables

Beacon Beacon UHF Radio UHF Radio

S - band Transmitter

S - band Transmitter

Magnetorquer Magnetorquer Magnetorquer Magnetorquer Magnetorquer Magnetorquer

Async . Serial SPI Power Discrete I/O HDLC

Legend

Building Canada’s Future In Space

The Missing Link:The Missing Link:ArcMinute Attitude Control

• Exploit CanX program and CanX-2 components for BRITE development.

• Operational science mission not possible without 3-axis control afforded by reaction wheels and star trackers.

• Dynacon Inc. providing “nanowheels” and “nano star tracker” based on successful ACS products used in MOST.

• Star tracker collocated with telescope.

Building Canada’s Future In Space

BRITE Bus Alternatives

Figure : BRITE Bus Configuration Alternatives15-cm CubeSat Triple CubeSat

Building Canada’s Future In Space

BRITE Bus Design

BSP Instrument

Li-ion Battery

GPS Antenna (2)

Star Tracker

Reaction Wheels (3)

UHF Beacon Antenna (2)

S-Band Uplink Antenna (2)

S-Band Downlink Antenna (2)

ACS Computer

Main OBC

Power Subsystem

S-Band TX/RXUHF Beacon GPS Receiver

TJ Solar Cells

Aluminium Panel and Sub-frame

5 cm

Figure : BRITE Bus Exploded View

CanX-2 ComponentsWithDynaconNano ACS

32 kbps Downlink4 kbps Uplink

4 Wh Avg Generation3.5 Wh Avg Consumption

Telescope and Star Tracker likely same device

3 kg Total Mass

Building Canada’s Future In Space

BRITE Ground Stations

UTIAS/SFL, Toronto

UBC, Vancouver University of Vienna

Up to 6 MB/dayfor BRITE

MOSTGroundStation Network Science

Frequencies

Building Canada’s Future In Space

NanoSat Attitude Control• Boresight wander < 1 arcmin

(Boresight roll < 10 arcmin)

• Slew capability at 1°/sec

• Smearing through controlled0.1°/sec slews.

• 15-min observations consist of co-added 1s-1min exposures.

• 15 min between observations to change target fields. Up to 3 target fields/orbit.

• Inherited from MOST ACS, exploiting advances in smaller actuators and sensors. Must fit 0.8 kg, 0.9 W orbit average.

Safe Hold

Detumble

Coarse Pointing

Fine Pointing Bias Momentum

Passive Control

Figure : BRITE ACS Modes and Transitions

Reaction WheelsMagnetorquers

0 50 100 150 200-8

-6

-4

-2

0

2

4

6

arc-min

99 percentile = 4.5, 0.8, 0.7 arc-min

minutesRate SensorsMagnetometerCoarse Sun SensorStar Tracker

Building Canada’s Future In Space

Conclusion• BRITE (aka CanX-3) proposes to be among the first operational

science nanosatellites.

• BRITE stellar photometry to answer significant astronomical questions, mission complementary to MOST (bright stars with periods of oscillation from hours to weeks).

• Science objectives consistent with emerging capabilities of nanosats. Mission focused to fit capabilities.

• CanX program at UTIAS/SFL trains student teams under staff mentorship. Also allows aggressive experimentation in space.

• BRITE made possible by CanX-2 technology and Dynacon Nano ACS currently under development.

• BRITE = science + technology + education

• Target launch late 2006, early 2007.

Building Canada’s Future In Space

Natural Resources