STO Mission Highlights & GUSSTO Mission Concept Pietro Bernasconi JHU/APL

1. STO Mission Highlights & GUSSTO Mission Concept Pietro Bernasconi JHU/APL

2. STO & GUSSTO aim at answering following Long 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?

3. Galactic Plane Region Near l= 340 NOW @ 3 deg spatial resolution STO & GUSSTO • 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

4. STO Science Flight Configuration Electronics 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 Telescope Dewar RF Box Optics Box • 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 Sliding Weight

5. STO Observing Platform TDRSS high rate antenna Reaction wheel Spectrometer pressure vessel C&C computer pressure vessel Solar arrays Batteries stack CG telescope balance slider Wide field star camera 80-cm diam telescope Narrow field star camera Dewar SIP Dummy arrays Ballast hopper SIP solar arrays

6. 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

7. 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/h Bias drift: < 3 arcmin/h (-40 / +80°C)

8. 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

9. Star Tracker(s) • Camera: • Commercial: StarDotNetcam 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

10. STO Launch and flight Current location 1/25/2012 day 10 -77.2 lat -108.7 long Launch Site: McMurdo 1/15/2012 Predicted termination: 1/29/2012

11. In-Flight Pointing Stability Celestial tracking active 0.69 arcsec RMS 0.83 arcsec RMS

12. In-Flight Pointing Stability 0.42 arcsec RMS 0.75 arcsec RMS

13. Wide Field Star Tracker

14. Eta Carinae

15. Position knowledge ~ 2 arcsec mag 6.25 mag 5.92 mag 6.43 mag 6.23 mag 6.42 mag 5.38

16. 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

17. GUSSTO! Astrophysics balloon Mission of Opportunity selected for phase A concept study from the last round of ExploerMoO Star Cameras TDRSS Antennas Dewar Telescope 1 meter SIP • 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

18. Backup Slides

19. Ground Control Console

20. STO Communications 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) • Downlink • Telemetry: TDRSS (COM1) up to 92 kbit/sec • DATA & live video: 2CSBF LOS 1Mbit/sec • SP V & A, Gond. A: Science Stack 5 analog channels • UPLINK: • Commanding: TDRSS (COM1) • 5 Discrete commands: Science Stack • Master power ON, OFF • Slave power ON, OFF • Terminate

21. 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

22. 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

23. Solar Bolometric Imager (2001 – 2008)A mission to determine the causes of total solar irradiance variability • 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 NM • 2007: 1 day scientific flight, Fort Sumner NM