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Rama Asuri - Homework 3 (choice 1): Square Kilometre Array (SKA) usecase

Science goals

According to 2, here are the science goals -

  1. Galaxy Evolution, Cosmology And Dark Energy
  2. Strong-field tests of gravity using pulsars and black holes
  3. Probing the Cosmic Dawn
  4. The cradle of life
  5. Flexible design to enable exploration of the unknown

Galaxy Evolution, Cosmology And Dark Energy

Universe is expanding but not at a constant rate. It is accelerating. We don’t know the reason why it is expanding in the first place. We could understand the reasons for this expansion, if we can learn more about Hydrogen and dark matter.

Hydrogen is abundant throughout the Universe. It is considered to be the fuel for a star formation inside a galaxy. Seventy percent of the Sun is Hydrogen and Hydrogen atoms emit radio waves which makes the Sun and other stars some of the brightest objects in the cosmos.

SKA will help understand how galaxies form and evolve by detecting the Hydrogen across the Universe. As of today, we don’t have this kind of technology to detect farthest distance like edge of the Universe. SKA can detect new galaxy formations at the edge of the Universe 2.

Strong-field tests of gravity using pulsars and black holes

Einstein’s theory of relativity still holds true. SKA will test relativity principles where no exiting technology has ever accessed the regions of the Universe that is dark and far 1. Astronomers found quasars with the help of radio data 6.

The origin and evolution of cosmic magnetism

According to 3, cosmic magnetism is everywhere in the Space. Learning about magnetic fields help us understand the electric fields. The question is, where does the cosmic magnetism come from? We don’t know this but understanding cosmic magnetism definitely helps us learn more about the Universe from the time of Big Bang. Besides gravity, magnetism shapes the massive structures in the Universe 4.

Probing the Cosmic Dawn

SKA is the most sensitive radio telescope. It will go beyond the distance of 13 billion light years. Optical and infrared telescopes captured galaxies at a distance of 13 billion light years from earth. Even before that, there was a time where the Universe was dark up until the formation of the first galaxy. Radio Telescopes reach even when there is no light or light is being blocked9. SKA will provide insight into this early Universe before the formation of the first galaxy 1.

The cradle of life

There are two ways SKA can help find the extraterrestrial life. One way is to detect weak extraterrestrial radio signals if they were to exist. This will expand on the capabilities of projects such as search for extraterrestrial intelligence (SETI). Other way is to search for organic molecules in the outer space 5.

Flexible design to enable exploration of the unknown

We don’t know what we will be stumbling on while exploring the space. SKA is a high sensitivity radio detection. Optical and infrared has limitations due to dust or poor visibility. But Radio waves can be detected even without the light. Astronomers stumbled on asteroids hunting grounds in archived Hubble images 10.

Current status

There are 3 phases. Phase 1 provides ~10% of the total collecting area at low and mid frequencies by 2023 (SKA1). Phase 2 provides full array (SKA2) at low and mid frequencies by 2030 and Phase 3 will extend the frequency range up to 50Ghz [7].

Late last year, SKA successfully completed its System Critical Design Review. It also under went two additional reviews related to Operations and Management 8. At the of reviews, there were 250 observations and questions raised which resulted in 40 recommendations. SKAO accepted all 40 of those recommendations and currently being implemented. SKAO team fully understand the issues and challenges. It helped them quickly move to implementation stage. After successful completion of the reviews, decision makers approved the construction to start later this year(2020). Initially, COVID-19 threatened the review process but the reviews have completed on time as planned. This puts the SKA project on track with no delays. Based on the reviews outcome, SKAO team finalized the SKA’s Construction Proposal and Observatory Establishment and Delivery Plan [2].

SKAO team is putting together new governance structure and planning for the establishment of the Observatory later this year and for the commencement of SKA1 construction activities as early in 2021 as possible. According to Philip Diamond (SKA Director-General), they are taking various risk mitigation steps as a precautionary measure by laying down various failure scenarios. He also mentioned that this world’s major scientific endeavor will bring employment, innovation and scientific exploration to benefit partner countries [2].

Big data challenges of the SKA

The data is huge and storage will be a problem. To tackle this problem, data size must be reduced in real time. Only capture or filter relevant data and save it. Raw data generated would be around an exabyte a day and after compression, it will reduce to 10 petabytes per day. An Tao, head of the SKA group of the Shanghai Astronomical Observatory stated, “It will generate data streams far beyond the total Internet traffic worldwide.” [7].

Raw data is coming from everything that is being observed by SKA. This data is collected by an array of dish receivers located across different geographical locations around the world. In case of pulsars, this data is reduced to form astronomical images or temporal data [1].

Initially, the data is ran through quality checks and good data, free of radio frequency interference, is stored in the long term preservation system. Multiple copies of this data is save at different location as a backup. Later, post processing and data analysis is performed. Once the data analysis is done, it can be visualized. All of this data is also preserved for the long term. Every year, it is expected to generate 600 PB and store this data for the observatory lifetime which is projected to be 50 years. This is just for the phase 1 of the project. Phase 2 and phase 3 will increase the size of the day to even bigger scale. As the data gets processed, the velocity of the data goes down from Petabytes to Terabytes. There is also data that is coming from logs, calibrations, configurations, managing archival, simulation models related to the SKA itself. This data is used to run the SKA without failures or downtime. Images are stored into databases of sources and time series data [1].

Footnotes