STO Mission Highlights & GUSSTO Mission Concept Pietro Bernasconi JHU/APL.
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Transcript of STO Mission Highlights & GUSSTO Mission Concept Pietro Bernasconi JHU/APL.
STO Mission Highlights&GUSSTO Mission Concept
Pietro BernasconiJHU/APL
STO & GUSSTO aim at answering followingLong Standing Questions
How and where are interstellar clouds made, and how long do they live?Under what conditions do clouds form stars?How do stars return enriched material back to the Galaxy?How do these processes sculpt the evolution of galaxies?
Spectral diagnostics of the interstellar life cycle define a new, pressing need for large-scale, high resolution, THz spectroscopic surveys!
STO Implementation:• Map Milky Way in 2 important interstellar lines:• [CII] @ 158 mm, 1.9 THz• [NII] @ 205 mm, 1.45 THz
• ~ 1’ Spatial resolution• < 1km/s Velocity resolution
Galactic Plane Region Near l = 340
NOW @ 3 deg spatial resolution
STO & GUSSTO
STO Science Flight ConfigurationElectronics Box
RF Box
Telescope
Dewar
Sliding Weight
Optics Box
Telescope Specifications:– 1ary aperture: 80 cm– Length: ~1.2 m– F-ratio: F/17.5– ½ angle FOV: 3.5 arcmin– 1ary material: ULE glass
honeycombed– Weight: 420 lbs
— 2x4 Pixel HEB Mixer array— HEB mixers down-convert high
frequency sky signals to microwave frequencies
— Cryogenic System keeps FPA @ 4K with 100 l liquid He cryostat
Schottky Receiver for warm mission when cryogens exhausted
— Survey of [CI] @ 492 GHz
STO Observing Platform
Solar arrays
Spectrometer pressure vessel C&C computer
pressure vessel
Reaction wheel
Narrow field star camera
Wide field star camera
Dewar
80-cm diam telescope
CG telescope balance slider
Dummy arraysSIP
Ballast hopper
SIP solar arrays
TDRSS high rate antenna
Batteries stack
Summary Gondola Specifications Dimensions:
– Base foot print: 5.6 4.8 ft– Max width: 19.6 ft– Max depth: 8.6 ff– Max height: 14 ft
Weights (Antarctica):– Science (estimated): 2880 lbs– + CSBF equip (no ballast): 3550 lbs
Power:– Usage
• Average: ~ 400 W• Peak (transient): ~800 W
– Performance at float altitude (2012 flight):• > 1100 W peak power generation• > 5 hours autonomy without PV power • > 150 W with arrays back illuminated
Telemetry:– Commanding (via SIP):
• LOS: ~1 Mb/s• Over Horizon: 6 Kb/s
– Data downlink (via SIP):• LOS: ~1 Mb/s• Over Horizon: 92 Kb/s
Pointing System Pointing Requirements:
– Range:• Azimuth: 360 deg, but no closer than 30 deg to Sun• Elevation: 0 to 58 deg
– Acquisition Accuracy: < ±20 arcsec– Pointing Stability: < ±15 arcsec during time intervals ~ 10 min– Pointing Knowledge: < ±15 arcsec
APL developed pointing system• Azimuth-Elevation servo system (SBI heritage):
– Azimuth: Reaction wheel and Momentum Transfer Unit (MTU)
– Elevation: Direct drive motor directly mounted to telescope
• Attitude determination (NEW for STO):– In-house developed Start Tracker for accurate
pointing knowledge < 5 arcsec– 3 high precision and low drift single axis optical
gyroscopes. SRS2000 from Optolink LLC.
– 3 tilt sensors & 1 elevation encoder– Magnetometer: for coarse Azimuth knowledge:
~ 0.5 degree– Counterweight slider along telescope axis used
for compensating telescope CG shift due to change in He level during mission.
SRS2000 gyroscope
Angle random walk: < 1.8 arcsec/hBias drift: < 3 arcmin/h (-40 / +80°C)
Momentum Transfer Unit (MTU)
• Momentum Transfer Unit (MTU) steers entire gondola in azimuth• Torque exerted against reaction wheel• Angular momentum is “dumped” into the balloon to slow wheel when it spins too fast• Flight heritage: Flare Genesis, SBI, STO-test
balloon connection (ladder)
titanium shaftgondola frame
reaction wheel momentum dump Motor
thrust bearings
torque Motor
movable inner race motor for inner race
motor stator motor rotor
Star Tracker(s) Camera:
– Commercial: StarDot Netcam SC5– B&W chip: 2592x1944 pix– CPU with Linux Operating system– 10/100 base T Ethernet connectivity– In-house electronics modifications for operating in
vacuum environment at -40/+80 deg C
Optics:– 2 ST with different FOV– Wide field ST:
• Primary camera for high precision pointing knowledge
• 50 mm commercial lens• 7 deg FOV• Detects stars to ~ mag 6 in day-time at float alt.• ~ 5 arcsec position determination accuracy
– Narrow field ST• Secondary camera for single star identification &
tracking• 200 mm commercial reflector lens• 0.5 deg FOV• Detects stars to ~ mag 10 at float altitude & ~ 2
from the ground• Used also for ground testing of pointing system
– Light red filters to cut blue & green light– 55 inch long baffles to minimize stray light pollution
Mount:– 2 axis high precision kinematic mount– Side mounted to telescope– Both ST attached to common plate
Software:– In-house developed star identification code– Based on published voting algorithm– Camera detect dots (potential stars)– MAX3 computer identifies stars & determines
bore sigh pointing coordinates– Code improved following experience from
2009 test flight
STO Launch and flight
Launch Site:McMurdo1/15/2012
Current location1/25/2012 day 10-77.2 lat-108.7 long
Predicted termination:1/29/2012
In-Flight Pointing Stability
0.69 arcsec RMS
0.83 arcsec RMS
Celestial tracking active
In-Flight Pointing Stability0.42 arcsec RMS
0.75 arcsec RMS
Wide Field Star Tracker
Eta Carinae
Position knowledge ~ 2 arcsec
mag 6.43
mag 6.23
mag 6.25
mag 5.92
mag 5.38
mag 6.42
STO Flight Performance Summary Command & Control
Excellent control capability Autonomous science scheduler working nominally Some in-flight adjustments needed to correct behavior not predicted during testing
Communications & Telemetry Excellent LOS for ~ 30 hours Good OTH (up to 92 kb/s downlink) with some tweaking needed initially
Pointing Excellent pointing stability while in active tracking mode:
< 1 arcsec RMS Jitter in AZ and EL almost indefinitely < 4 arcsec peak-to-peak almost indefinitely & < 2 arcsec for up to 10 mins
Good pointing knowledge (preliminary): < 2 arcsecs when star camera fix available < 0.5 degrees without star camera fixes Star camera fixes every 2 to 5 minutes. Use gyro information between fixes
Power ~ 1100 W peak power generation ~ 350 - 400 W average power requirement
Instrument Dewar held THz detectors at < 6K for ~ 6 days Thereafter in “warm” mission mode with 493 GHz room temp receiver
Thermal All temperatures as expected/predicted & within operating range
TDRSS Antennas
Telescope 1 meter
Star Cameras
Dewar
SIP
GUSSTO!Astrophysics balloon Mission of Opportunity selected for phase A concept study from the last round of Exploer MoO
• 1-m aperture off-axis gregorian telescope• > 100 days lifetime with 24hr/day operation• Fully autonomous operations when beyond Line of Sight contact• Pointing: ~5 arcsec knowledge and accuracy, < 5 arcsec RMS Jitter, smooth tracking of objects in the sky• Provide up to 2KW of peak power from solar array & Li-Ion battery system• Total observatory mass ~2750 lbs. Includes CSBF SIP, antennas, solar arrays, and 135 kg ballast• Communications provided via CSBF SIP: LOS with UHF @ 1Mb/s, OTH with TDRSS @ 150 kb/s
Backup Slides
Ground Control Console
STO Communications
• Downlink– Telemetry: TDRSS (COM1) up to 92 kbit/sec– DATA & live video: 2CSBF LOS 1Mbit/sec– SP V & A, Gond. A: Science Stack 5 analog channels
STO relies on SIP and NSBF’s OCC and ROCC for communications to/from science payload
System fully tested with STO test flight.
Fully tested during hang test (August 16, 2011)
• UPLINK:– Commanding: TDRSS
(COM1)– 5 Discrete commands: Science Stack
• Master power ON, OFF• Slave power ON, OFF• Terminate
Power System• Power Requirement– Operating Voltage: 24V– Average Power: 700 Watts– Peak Power: 1400 Watts (transient)
• Strong heritage from SBI & FGE• Two 12 V Sealed Lead Acid Batteries
– Model: ODYSSEY SLI PC1700– Strong flight heritage– 65 Ah capacity– -40C to +80C operating Temp
• Charge Controller– Originally built by MEER for FGE
and re-used for SBI– Refurbished for STO– Peak Power Tracker (NEW)
• Discrete commands from SIP– Via Science Stack– Master ON/OFF– Slave ON/OFF
• Solar Arrays:– 480 A300 Cells by Sun Power Corp.
– 21.5% efficiency– Balloon flight heritage
– 1100 Watts @ float altitude
• Solar Panels:– 6 panels on same side of gondola (Right side)
– 2 rows of 3 panels– Each panel has 80 cells
– Manufactured by SunCat Solar– Polymer laminate on honeycomb substrate– Aluminum angles frame
• Dummy panels on Left side of gondola– For weight balance– To have symmetric wind effects
Flare Genesis Experiment (1992 – 2001)A mission to determine the triggering mechanism of solar flares
• Gondola dimensions:– Base foot print (WDH): 6 5 14 ft (with SA 20 9 15 ft)– Weight: ~ 3500 lbs
• Sun pointing system:– Alt-azimuth:
• Telescope mounted on elevation axis• Azimuth pointing by turning whole gondola with a reaction wheel
– 3 stages gondola pointing control:• Coarse: 4 photodiode at 90° intervals around the gondola.• Intermediate: 2 linear sensors with cylindrical lenses parallel to
elevation and azimuth. FOW: ±20°, accuracy ~ 0.25°.• Fine: small telescope projecting a solar image onto a lateral-effect
diode (LED). FOW ±1°, accuracy ~ 0.05" RMS when Sun is at the center of LED.
• Fine pointing accuracy: ~ 8 – 10 arcsec
– Image stabilization system to keep image stable to < 1 arcsec at CCD image plane
• Autonomous Command & Control Computers:– 2 computers to autonomously carry out observations without commands
from ground for up to 15 days
• Power system: Solar arrays producing ~ 1KW• Telemetry: Provided by NASA• Stratospheric flights @ 120,000 ft altitude :
1994: 1 day test flight, Fort Sumner NM
1996: 19 days engineering flight, Antarctica
2000: 17 days scientific flight, Antarctica
• Same Gondola as Flare Genesis Experiment (refurbished)• Payload:
– Specialized 20-cm diameter solar telescope– Bolometric Imaging Camera
• New mount developed for installation of new telescope• Pointing:
– Same as FGE with upgrades and improvements• Improved pointing performance: now ~ +/- 5 arcsecs jitter
– Telescope mount with passive damping system to filter out gondola residual jitter
• Autonomous Command & Control Computers:– Same design as FGE but with upgrades and improvements– New hardware for two C&C computers– Improved software for autonomous control
• Power system:– Same design as FGE but with upgrades and improvements– New generation solar cells producing ~ 720W
• Stratospheric Flights @ 120,000 ft altitude:2003: 1 day engineering and scientific flight, Fort Sumner NM2007: 1 day scientific flight, Fort Sumner NM
Solar Bolometric Imager (2001 – 2008)A mission to determine the causes of total solar irradiance variability