ALMA Data Transmission System Upgrade Begins 

13 March, 2023 / Read time: 4 minutes

In 2018, ALMA published the strategic vision for development towards enhancing the telescope capabilities in the 2030s as the ALMA Development Roadmap. The priority identified in this vision is to broaden the Intermediate Frequency (IF) bandwidth receiver by at least a factor of two and to upgrade the associated electronics and the Correlator. This upgrade is now known as the ALMA2030 Wideband Sensitivity Upgrade (WSU). In November 2022, the ALMA Board approved project proposals for the development of a second-generation correlator led by the National Radio Astronomy Observatory (NRAO) from the United States and a new data transmission system (DTS) led by the National Astronomical Observatory of Japan (NAOJ). 

Implementing the ALMA2030 WSU will revolutionize astronomical research by enhancing the telescope’s performance. Moreover, the substantial increase in IF bandwidth will lead to a dramatic surge in scientific data collected during each observation session, significantly advancing research efficiency. 

However, the significant amount of data will challenge the data transmission system (DTS), which transmits the obtained data from each antenna to the Correlator and total-power spectrometer and the brains to analyze it. To proceed with the ALMA2030 WSU, the DTS needs to be upgraded. 

In today’s advanced information society, ethernet is one of the most common channels for digital communication, and it is the one that we often hear about and mostly use in our daily lives. So far, ALMA has used its own communication systems, different from those used in everyday life. However, this causes inconveniences such as the inability to obtain replacement components when a problem occurs quickly. To avoid this, the DTS upgrade will be based on ethernet. It will rely on the most advanced, readily commercially available standard, 400 GbE (Gigabit per second ethernet). Combining multiple 400 Gbps (Gigabit per second) high-speed ethernet lines, a high-speed transmission system will be designed to transmit up to 1200 Gbps data from each antenna to the Correlator. Using the 400 GbE long-range option will enable the transmission of data over distances of approximately 80 kilometers, which would allow for an increase in the maximum distance between antennas in the future. This, in turn, would enhance the angular resolution of ALMA, resulting in a sharper and more powerful telescope. 

 
What does the upgrade bring? 

Celestial bodies contain various atoms and molecules, each emitting radio waves at different frequencies. For example, carbon monoxide molecules emitting radio waves at 115 GHz indicate rarefied gases with low temperatures and densities floating throughout space. Conversely, hydrogen cyanide, which emits radio waves at 89 GHz, is known as an indicator of a relatively hot and dense gas. By comparing the distribution of these two molecules, we can explore how stars are born from environments with rarefied gas. In this way, various astronomical phenomena are revealed by observing many kinds of molecules simultaneously. Simultaneous observation of many different types of molecules means simultaneous observation of radio waves in a wide frequency band. However, observing a wide frequency band at once is technically challenging. Currently, observations are carried out many times to cover a wide frequency band, divided into narrow frequency bands, which requires much observation time. 

By improving receivers to observe a wide frequency band at once and having an improved DTS to transmit all that data simultaneously, observing and analyzing radio waves on a broader frequency band with high sensitivity with the same observation time as before will be possible. New discoveries that have never been captured before are expected. 

Additional information

The original press release was published by the National Astronomical Observatory of Japan (NAOJ), an ALMA partner on behalf of East Asia.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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