TIM (Terahertz Intensity Mapper)

TIM is the acronym for Terahertz Intensity Mapper with the goal of demonstrating balloon-borne FIR spectroscopy limited by the photon noise from the atmosphere. TIM will be a vital technological, data analysis, and scientific steppingstone to future orbital missions, and will also advance the understanding of galaxy evolution through observations that cannot be replicated with current FIR instruments. The instrument was built through an extensive cooperation lead by the University of Illinois and the collaboration of the University of Pennsylvania, NASA's Jet Propulsion Laboratory, Arizona State University, University of Arizona, California Institute of Technology, Harvard Smithsonian Center for Astrophysics, John Hopkins University, University of Florida, University of Chicago, Rutgers University, from the United States, Max Planck Institute for Astronomy from Germany and the Laboratoire d'astrophysique de Marseille from France.

At left we can see an scheme of the TIM payload (click to enlarge). It combines a long-slit spectrometer operating from 240 µm to 420 µm with a 2 meters low-emissivity carbon-fiber telescope to provide a substantial increase in sensitivity over existing instruments.

The TIM telescope is a reflecting telescope with a segmented, 2.0-meter diameter, carbon fiber primary mirror, as well as a fully carbon fiber secondary and support structure, with gold metallization of the reflecting surfaces to minimize the emissivity. To efficiently perform spectroscopy over the full 240 µm to 420 µm band, TIM counts with two independent spectrometer modules: a short wavelength module covering 240 to 317 µm, and a long wavelength module covering 317 to 420 µm. Both modules follow the same basic design consisting of a plane diffraction grating mounted between concave collimating and camera mirrors in a Czerny- Turner configuration.

The detectors are formed by arrays of Kinetic-Inductance Detectors (KID) which emerged in the last decade as a straightforward approach to very large detector arrays for astrophysics. These devices use thin-film, high-Q micro-resonators that absorb incident radiation and respond by changing resonance frequency and line-width. The TIM cryostat and cryogenic design was based on BLAST-TNG, another balloon-borne telescope which builds from the flight heritage of BLAST and BLASTpol. The design is intended to hold for 28 days, long enough for an long duration balloon flight in Antarctica.

TIM gondola and pointing system was designed also around the successful BLAST heritage. It consists of a precision-pointed inner frame (composed of the primary, secondary, near-field baffle, and cryostat) supported by an external gondola. The outer frame is pointed in azimuth by a flywheel and an active pivot. The inner frame has an elevation mount with direct drive servo motors driving it relative to the outer frame. Balance of the inner frame is maintained by pumping liquid from the bottom of the frame to the top to compensate for cryogen boil-off. The attitude determination system uses an array of pointing sensors including two sophisticated star cameras, two sets of fast, low-drift gyroscopes, a quad-GPS system, a digital Sun sensor, encoders, tilt sensors, and a magnetometer.

Balloon launched on: 9/23/2024 at 13:28 UTC
Launch site: Scientific Flight Balloon Facility, Fort Sumner, (NM), US  
Balloon launched by: Columbia Scientific Balloon Facility (CSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon  
Flight identification number: 747N
End of flight (L for landing time, W for last contact, otherwise termination time): 9/24/2024 at 21:36 UTC
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 8 h
Landing site: In Deaf Smith County, Texas, US

• TIM website University of Illinois
• NASA to Launch 8 Scientific Balloons From New Mexico NASA website
• The Terahertz Intensity Mapper (TIM): a Next-Generation Experiment for Galaxy Evolution Studies 30th International Symposium on Space THz Technology, Gothenburg, Sweden, April 15-17, 2019