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 NGC 1333 Serpens Cep CW NGC 7029 24 February 2014 NGC 2071 BETTII: FISICA Workshop 7 Spectra of Cores Herschel beam Herschel sees a blend of multiple sources Partially embedded disk system 24 February 2014 Deeply embedded YSO BETTII: FISICA Workshop YSO with Water Ice Feature at 43 µm 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 24 February 2014 Warm Delay BETTII: FISICA Workshop TerTary 13 The Telescope Assembly Primary Secondary Flat TerTary 24 February 2014 BETTII: FISICA Workshop 14 The Instrument • Double-Fourier instrument LHe Tank – FIR channel for science – NIR channel for angle tracking and fringe tracking (maybe) LN2 Tank He3 Fridge Science/FIR Volume (4K) • 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 – Cold delay line Delay Line Collimated input beam – FIR beam splitter – FIR dichroics Long #1 Short #1 Detector Detector Long #2 Asphere Tracking Channel Short #2 Near-IR dichroics 24 February 2014 Asphere Optical Relay 50/50 OAPs Far-IR dichroics Beam Splitter BETTII: FISICA Workshop Detector Detector 16 The Layout Detector Arrays Dichroic Cold Delay line Cold Pupil 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 • 24 February 2014 Undergraduate Students D. Leisawitz • • S. Maher • L. Mundy • M. Rizzo R. Silverberg • J. Staghun • • T. Veach M. Griffin L. Spencer G. Savini A. Kogut J. Mather • • • • • • 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) BETTII: FISICA Workshop 22
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