People Working for ALMA (2) Computing Work Connects Machines as well as People
What is Computing All About?
— Let’s start with a very basic question; what is computing all about?
Kosugi: To put it shortly, ALMA computing team conducts various software developments for making the ALMA telescope actually work.
— You are making software, not hardware like computer devices.
Kosugi: Right. The word “software” probably reminds most people of programs available on personal computer.
— Games and applications.
Kosugi: Exactly. Even if we have a computer like PC or smartphone, we cannot use it without software. Similarly, ALMA has supercomputers called “Correlator” in Chile. Enhanced computing capability is required for ALMA that processes enormous amounts of data to produce images of astronomical objects from data collected by up to 66 antennas. And such processing is carried out by the correlators. Our ALMA computing team develops software to control the Correlator and other types of software too.
— What other types of software are you making?
Kosugi: ALMA has roughly two types of software: one is “online software” which is used to operate observing instruments and systems in real time for actual observations. And another is “offline software” which is used before or after observation. For example, online software includes control software to make up to 66 antennas work in perfect order and software to send commands to the Receiver that has a measurement function of radio waves collected by antennas. Also, online software includes software to operate the Correlator that processes data from multiple antennas and software to store the data processed by the Correlator into the archives.
Computing Builds Framework of ALMA
— On the other hand, what is the offline software?
Kosugi: To explain it, we need to begin with the introduction of the flow of observation with ALMA. First of all, researchers prepare observing proposals and submit them to the ALMA Observatory. When the proposal is accepted after the review, researchers describe various setting parameters for telescope and instrument in a set of electric files (so-called “Phase 2 Programs”) and send the Programs to the database. And then, ALMA operators execute the Phase 2 Programs on the ALMA control computers to perform observations. In this process, various pieces of offline software are used: such as software to prepare observing proposals; software to support the proposal review; and software to prepare Phase 2 Programs.
— I see.
Kosugi: Offline software is used again after an observation has been finished and the data has been archived. ALMA staffs process the data and the resulting data is back to the archive. Then finally, the data is sent to the researcher who submitted the observing proposal. The software for data processing and archiving are also categorized as offline software. Each piece of function required for the observation flow is developed by the computing team.
— It looks like computing is building the framework of the ALMA observatory.
Kosugi: Most people think of astronomers as the image of people working for ALMA. On the other hand, our computing work is not visible to the public because we are playing “background” roles. I hope these interviews will help highlight the importance of computing and raise the motivation of the computing team members.
— How many people are working in your computing team currently?
Kosugi: In ALMA as a whole, three regions have each computing team respectively in Japan, North America, and Europe and one computing team in Chile. There are approximately 80 members in total all over the world, of which nearly 20 members belong to the Japanese computing team. I lead the Japanese computing team as a manager.
— Does each regional team have different tasks?
Kosugi: Main task assigned to the Japanese team is software development to control the Atacama Compact Array (ACA, as known as the Morita Array) and its Correlator. Also we implement some tasks jointly with other regional teams in the development of analysis software and archive software as well as in the tests of software.
— ALMA has already started observations but is the development still in progress?
Kosugi: ALMA has been continuously improving its capability by installation of new observing instruments and addition of new observing modes. Even for the Correlator mentioned earlier, discussion for the next generation development has already started. Our computing team has also been continuing development to catch up with these ongoing developments. For example, when a new observing mode is added, such function needs to be included in software. And, we need debugging too. Bugs have never been worked out in such a large scale software. In addition to the development of software functions, we are always conducting development while thinking about how to improve the speed and efficiency of software. If data analysis needs to be faster, we try to make it better by algorithm improvement or parallelization of analysis software.