The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) Dr. Stephen Rinehart NASA s Goddard Space Flight Center Laboratory for Observational Cosmology
What is BETTII? As proposed, BETTII looked something like this 24 February 2014 BETTII: FISICA Workshop 2
Evolution By December 2012, the design looked like 24 February 2014 BETTII: FISICA Workshop 3
Current Design And now (February 2014) Siderostat Dewar Primary Telescope Assembly Exoskeleton Metering Truss Essential design elements are unchanged 24 February 2014 BETTII: FISICA Workshop 4
What can it do? 24 February 2014 BETTII: FISICA Workshop 5
Key Science Features 8-meter baseline + Double-Fourier = Angular Resolution of ~0.5 at 40 µm Spectral Resolution of up to R~200 Wavelength Coverage from 30-90 µm Sensitivity: ~20 Jy in 10 minutes The Negative Spin: Require bright targets The Positive Spin: Can do targets that saturate for Spitzer and Herschel 24 February 2014 BETTII: FISICA Workshop 6
Science Goals Cep CW NGC 1333 Serpens NGC 7029 NGC 2071 24 February 2014 BETTII: FISICA Workshop 7
Spectra of Cores Herschel beam Herschel sees a blend of multiple sources Partially embedded disk system Deeply embedded YSO YSO with Water Ice Feature at 43 µm 24 February 2014 BETTII: FISICA Workshop 8
A Tale of Three Systems Instrument/Cryostat External OpTcs Control System (Exoskeleton) 24 February 2014 BETTII: FISICA Workshop 9
Metering Truss Must be stiff, strong, and light Made of carbon fiber tubes with stainless steel nosecones and nodes 24 February 2014 BETTII: FISICA Workshop 10
The Completed Truss Light (~70kg) Strong can take a 10g load with factor of 2 margin Stiff: first mode at 23.0 Hz. 24 February 2014 BETTII: FISICA Workshop 12
External Optics 8 meters Primary Flat Secondary K- mirror Warm Delay TerTary 24 February 2014 BETTII: FISICA Workshop 13
The Telescope Assembly Primary Secondary TerTary Flat 24 February 2014 BETTII: FISICA Workshop 14
The Instrument LHe Tank LN2 Tank He3 Fridge Science/FIR Volume (4K) Double-Fourier instrument FIR channel for science NIR channel for angle tracking and fringe tracking (maybe) TES Bolometer Arrays (BUGs) Tracking/NIR Volume (77K) 24 February 2014 BETTII: FISICA Workshop 15
Instrument Optics Key features of the internal optics: Optical relay for cold pupil FIR beam splitter Cold delay line FIR dichroics Collimated input beam Near-IR dichroics Tracking Channel Optical Relay Delay Line 50/50 Beam Splitter OAPs Far-IR dichroics Long #1 Short #1 Long #2 Short #2 Asphere Detector Detector Asphere Detector Detector 24 February 2014 BETTII: FISICA Workshop 16
The Layout Detector Arrays Dichroic Cold Pupil Cold Delay line Relay Optics 24 February 2014 BETTII: FISICA Workshop 17
Opto-Mechanical 24 February 2014 BETTII: FISICA Workshop 18
The Control System Exoskeleton Computers Housekeeping 24 February 2014 BETTII: FISICA Workshop 19
Control Scheme Momentum dump ACTUATION LOOP CCMG wheel angle Siderostat Rotation stages Conversion to elevation and cross-elevation errors Elevation error Warm delay line CCMG Cross-elevation error Attitude error Slew mode SENSOR LOOPS Tracking mode 24 February 2014 Target pixel for guide star Tip/Tilt Position Target velocity and position Tip/Tilt mirrors Angle Sensor Gyros & star camera BETTII: FISICA Workshop 20
Overall Status Proceeding well: upcoming milestones Cryostat complete by April 2014 Internal optics installed and aligned by August 2014 Detector delivery in June 2014 Detector testing/characterization through August 2014 Delivery of telescope assemblies in August 2014 (!!!) Alignment of external optics by November 2014 Control system testing ongoing Performing better than expected! On track for launch in Fall 2015 from Fort Sumner 24 February 2014 BETTII: FISICA Workshop 21
Thanks The BETTII Team: R. Barry D. Benford P. Calhoun W. Danchi A. Dhabal D. Fixsen C. Jhabvala UK Collaborators: P. Ade E. Pascale R. Juanola-Parramon Collaborators: R. Lyon D. Leisawitz S. Maher L. Mundy M. Rizzo R. Silverberg J. Staghun T. Veach M. Griffin L. Spencer G. Savini A. Kogut J. Mather Undergraduate Students J. Doiron S. Gore B. Hoffman W. Tierney R. Curley T. Kale T. Handleton S. Shapoval M. Canaparro D. Andrade J. Stokes C. Gibbons J. Gibson S. Weinreich J. Alcorn A. Rau S. Padder P. Nehme L. Oliveira H. Spooner C. Wagner A. Cotto N. Mihalko Y. Okafor P. Taraschi Y. Huertes-Morales And the Far- Infrared Telescope Experiment (FITE) team in Japan (H. Shibai, PI) 24 February 2014 BETTII: FISICA Workshop 22