Overview and status of EXCLAIM, the experiment for cryogenic large-aperture intensity mapping

The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a balloon-borne far-infrared telescope that will survey star formation history over cosmological time scales to improve our understanding of why the star formation rate declined at redshift z < 2, despite continued clustering of dark matter. Specifically, EXCLAIM will map the emission of redshifted carbon monoxide and singly ionized carbon lines in windows over a redshift range 0 < z < 3.5, following an innovative approach known as intensity mapping. Intensity mapping measures the statistics of brightness fluctuations of cumulative line emissions, as opposed to detecting individual galaxies, thus enabling a blind, complete census of the emitting gas. To detect this emission unambiguously, EXCLAIM will cross-correlate with a rich spectroscopic galaxy catalog. The EXCLAIM mission will use a cryogenic design to cool the telescope optics to approximately 1.7 K. The telescope will feature a 90-cm primary mirror to probe spatial scales on the sky from the linear regime up to shot-noise-dominated scales. The telescope optical elements will couple to six µ-Spec spectrometer modules, operating over a 420-540-GHz frequency band with a spectral resolution of 512 and featuring Microwave Kinetic Inductance Detectors (MKIDs). In the baseline design, the detectors will be read out with a Radio Frequency System-on-Chip (RFSoC). The cryogenic telescope and the sensitive detectors will allow EXCLAIM to reach high sensitivity in spectral windows of low emission in the upper atmosphere. Here, an overview of the mission design and development status since the start of the EXCLAIM project in early 2019 is presented.