The ALMA2030 Wideband Sensitivity Upgrade

John Carpenter, Crystal Brogan, Daisuke Iono, Tony Mroczkowski

Submitted on 31 October 2022


The Wideband Sensitivity Upgrade (WSU) is the top priority initiative for the ALMA2030 Development Roadmap. The WSU will initially double, and eventually quadruple, ALMA's system bandwidth and will deliver improved sensitivity by upgrading the receivers, digital electronics and correlator. The WSU will afford significant improvements for every future ALMA observation, whether it is for continuum or spectral line science. The continuum imaging speed will increase by a factor of 3 for the 2x bandwidth upgrade, plus any gains from improved receiver temperatures. The spectral line imaging speed will improve by a factor of 2-3. The improvements provided by the WSU will be most dramatic for high spectral resolution observations, where the instantaneous bandwidth correlated at 0.1-0.2 km/s resolution will increase by 1-2 orders of magnitude in most receiver bands. The improved sensitivity and spectral tuning grasp will open new avenues of exploration and enable more efficient observations. The impact will span the vast array of topics that embodies ALMA's motto "In Search of our Cosmic Origins". The WSU will greatly expand the chemical inventory of protoplanetary disks, which will have profound implications for how and when planets form. Observations of the interstellar medium will measure a variety of molecular species to build large samples of clouds, cores and protostars. The WSU will also enable efficient surveys of galaxies at high redshift. The first elements of the WSU will be available later this decade, including a wideband Band 2 receiver, a wideband upgrade to Band 6, new digitizers and digital transmission system, and a new correlator. Other upgrades are under study, including the newly developed ACA spectrometer and upgrades to Bands 9 and 10. The gains enabled by the WSU will further enhance ALMA as the world leading facility for millimeter/submillimeter astronomy. [Abridged]


Comment: 59 pages, 36 figures; ALMA Memo 621 at

Subjects: Astrophysics - Instrumentation and Methods for Astrophysics; Astrophysics - Cosmology and Nongalactic Astrophysics; Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Astrophysics of Galaxies; Astrophysics - Solar and Stellar Astrophysics


Simplified overview of the ALMA signal chain post-WSU upgrade. Components that are either new or will be upgraded are shown in blue (Credit for inset graphics and images: ALMA (ESO/NAOJ/NRAO)).