The Emirates Main Belt Infrared Spectrometer (EMBIRS) onboard the Emirates Mission to the Asteroid Belt

The Emirates Main Belt Infrared Spectrometer (EMBIRS), one of four remote sensing instruments onboard the Emirates Mission to the Asteroid Belt (EMA), is designed to collect data on six main-belt asteroid flybys, ending with proximity operations at 269 Justitia. EMBIRS will measure the emitted spectral radiance of these asteroids providing constraints on the thermophysical properties and spectral character/composition of these asteroids. In combination with the other instruments on the EMA payload, EMBIRS will address the key goals of the mission, specifically evaluating the origins and evolution of water-rich asteroids and their resource potential. EMBIRS measurements address several mission science objectives, including mapping the silicate mineralogy of compositionally diverse, water-rich asteroids, supporting the evaluation of their geologic history, and characterizing the temperature and thermophysical properties of multiple asteroids to assess their formation, surface evolution, and volatile histories.

The EMBIRS instrument is an interferometric thermal infrared spectrometer developed and provided by Northern Arizona University (NAU) and Arizona State University (ASU) in partnership with the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics for inclusion on the United Arab Emirates Space Agency’s EMA mission. It builds on a long heritage of thermal infrared spectrometers designed, built, and managed by ASU's Mars Space Flight Facility. EMBIRS is most directly akin to the Emirates Mars Infrared Spectrometer (EMIRS) on the Emirates Mars Mission (EMM). EMBIRS is a build to print of EMIRS except for minor modifications to the mechanical and thermal interfaces (Figures 1 & 2). EMBIRS is 53x29x32 cm, has a mass of ~12.7 kg, and requires 21 W during operational activities. EMBIRS collects spectral data from 6-40+ µm at 10 and 20 cm^-1 spectral sampling. This instrument utilizes an on-axis deuterated L-alanine doped triglycine sulfate (DLaTGS) detector and a scan mirror to make infrared radiance measurements of the asteroids during flybys and 269 Justitia proximity operations.

Under the current concept of operations, EMBIRS achieves complete global coverage (daytime and nighttime observations) of 269 Justitia within 8 weeks of observing with pixel sizes of <500 m/pixel and emission angles <30˚ (Figure 3). This observation strategy uses a set of pre-canned commands that set the calibration frequency, where space and internal calibration are used to obtain a full aperture calibration on-orbit every 30 minutes. During flyby operations, EMBIRS observes the surface of target asteroids using multiple methods to maximize spatial coverage.  This is accomplished via direct-stare observations for ~10 hours on approach and ~2 hours on departure with ~10-20 minute rasters during the closest approach. Parameters for these close-approach rasters are set by the flyby velocity and object size (Figure 4). EMBIRS is currently undergoing final design changes with assembly, integration, and environmental test that began in November 2024 and delivery to the spacecraft in August 2026.

Figure 1: Fully assembled EMIRS instrument on EMM prior to delivery to the spacecraft (Edwards et al., 2021). EMBIRS is build-to-print, using flight spare hardware from the EMIRS program, with the small interface changes to the mounting interface and thermal control.

Figure 2: The EMBIRS instrument and optical design is identical to the EMIRS instrument with minor changes to the metrology assembly to facilitate alignment (Edwards et al., 2021).

Figure 3: Planned EMBIRS coverage of 269 Justitia (top) after 1 week and (bottom) 8 weeks of observing.

Figure 4: Example flyby coverage from EMIRS observations of Deimos (Edwards et al., 2023).

 

References:

Edwards, C., Osterloo, M., Fisher, C., Jeppesen, C., Smith, N., Holsclaw, G., Wolff, M., Jonees, A., Knavel, J., & Pilinski, E. (2023). The First Observations of Deimos from the Emirates Mars Mission (EMM) Flybys. Paper presented at the European Geophysical Union.

Edwards, C. S., Christensen, P. R., Mehall, G. L., Anwar, S., Tunaiji, E. A., Badri, K., Bowles, H., Chase, S., Farkas, Z., Fisher, T., Janiczek, J., Kubik, I., Harris-Laurila, K., Holmes, A., Lazbin, I., Madril, E., McAdam, M., Miner, M., O’Donnell, W., Ortiz, C., Pelham, D., Patel, M., Powell, K., Shamordola, K., Tourville, T., Smith, M. D., Smith, N., Woodward, R., Weintraub, A., Reed, H., & Pilinski, E. B. (2021). The Emirates Mars Mission (EMM) Emirates Mars InfraRed Spectrometer (EMIRS) Instrument. Space Science Reviews, 217(7), 77. doi: 10.1007/s11214-021-00848-1