28-Nov-2022: India's SARAS radio telescope provides astronomers clues to the nature of Universe's first stars and galaxies
Scientists have determined properties of radio luminous galaxies formed just 200 million years post the Big Bang, a period known as the Cosmic Dawn thus providing an insight to the properties of the earliest radio loud galaxies that are usually powered by supermassive black holes.
Humans in their curiosity about how the early stars and galaxies formed and what they looked like have tried to capture the faint signals arising from the depths of the cosmos through a number of ground and space-based telescopes peering into the sky for a better understanding of the Universe.
Shaped Antenna measurement of the background Radio Spectrum 3 (SARAS) telescope -- indigenously designed and built at Raman Research Institute -- was deployed over Dandiganahalli Lake and Sharavati backwaters, located in Northern Karnataka, in early 2020.
In a first-of-its-kind work, using data from SARAS 3, researchers from the Raman Research Institute (RRI), Bengaluru, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia, along with collaborators at the University of Cambridge and the University of Tel-Aviv, estimated the energy output, luminosity, and masses of the first generation of galaxies that are bright in radio wavelengths.
Scientists study the properties of very early galaxies by observing radiation from hydrogen atoms in and around the galaxies, emitted at a frequency of approximately 1420 MHz. The radiation is stretched by the expansion of the universe, as it travels to us across space and time, and arrives at Earth in lower frequency radio bands 50-200 MHz, also used by FM and TV transmissions. The cosmic signal is extremely faint, buried in orders of magnitude brighter radiation from our own Galaxy and man-made terrestrial interference. Therefore, detecting the signal, even using the most powerful existing radio telescopes, has remained a challenge for astronomers.
Results from the paper by Saurabh Singh from RRI and Ravi Subrahmanyan from CSIRO published in the journal Nature Astronomy on November 28, 2022, have described how even non-detection of this line from the early Universe can allow astronomers to study the properties of the very first galaxies by reaching exceptional sensitivity.
"The results from the SARAS 3 telescope are the first time that radio observations of the averaged 21-centimeter line have been able to provide an insight to the properties of the earliest radio loud galaxies that are usually powered by supermassive black holes," said Subrahmanyan, former director of RRI and currently with Space & Astronomy CSIRO, Australia, and an author of the paper. “This work takes forward the results from SARAS 2, which was the first to inform the properties of earliest stars and galaxies.”
"SARAS 3 has improved our understanding of astrophysics of Cosmic Dawn, telling us that less than 3 percent of the gaseous matter within early galaxies was converted into stars, and that the earliest galaxies that were bright in radio emission were also strong in X-rays, which heated the cosmic gas in and around the early galaxies," said Singh, one of the authors of the paper titled 'Astrophysical Constraints from the SARAS 3 non-detection of the Cosmic Dawn Sky-Averaged 21 cm Signal'.
In March this year, Singh, along with Subrahmanyan and SARAS 3 team, used the same data to reject claims of the detection of an anomalous 21-cm signal from Cosmic Dawn made by the EDGES radio telescope developed by researchers from Arizona State University (ASU) and MIT, USA. This refusal helped restore confidence in the concordant model of cosmology that was brought into question by the claimed detection.
In March this year, Singh, along with Subrahmanyan and SARAS 3 team, used the same data to reject claims of the detection of 21-cm signal from Cosmic Dawn made by the EDGES radio telescope developed by researchers from Arizona State University (ASU) and MIT, USA.
"We have now got constraints on the masses of the early galaxies, along with limits on their energy outputs across radio, X-ray, and ultraviolet wavelengths," Singh noted. Further, using a phenomenological model, SARAS 3 has been able to put an upper limit to excess radiation at radio wavelengths, lowering existing limits set by the ARCADE and Long Wavelength Array (LWA) experiments in the US.
"The analysis has shown that the 21-cm hydrogen signal can inform about the population of first stars and galaxies ", shared another author, Dr. Anastasia Fialkov from the Institute of Astronomy, University of Cambridge. "Our analysis places limits on some of the key properties of the first sources of light, including the masses of the earliest galaxies and the efficiency with which these galaxies can form stars," said Fialkov.
Since its last deployment in March 2020, SARAS 3 has undergone a series of upgrades. These improvements are expected to yield even higher sensitivity towards detecting the 21-cm signal. Currently, the SARAS team is assessing several sites in India for its next deployment. "These sites are fairly secluded and pose several logistical challenges for deployment. However, they seem promising from science's viewpoint and, with new upgrades, seem ideal for our experiment", adds Yash Agrawal, a member of the SARAS team.
26-Nov-2022: PSLV-C54/EOS-06 Mission is accomplished
ISRO’s work horse PSLV-C54 has successfully launched EOS-06 satellite along with Eight Nano-satellites into two different SSPOs. The mission was accomplished from Satish Dhawan Space Centre SHAR on 26th November 2022.
EOS-06 is third generation satellite in the Oceansat series, which provides continued services of Oceansat-2 with enhanced payload capability. The satellite onboard carries four important payloads viz. Ocean Color Monitor (OCM-3), Sea Surface Temperature Monitor (SSTM), Ku-Band Scatterometer (SCAT-3), ARGOS. The Oceansat-2 which was a launched during Sept-2009 configured to cover global oceans and provide continuity of ocean colour data with global wind vector and characterization of lower atmosphere and ionosphere. The mission resulted in many research collaborations nationally and internationally on various areas global chlorophyll distribution, Kd 490 distribution, ocean color images, oil spillages, wind vector products.
The EOS-06 is envisaged to observe ocean color data, sea surface temperature and wind vector data to use in Oceanography, climatic and meteorological applications. The satellite also supports value added products such as potential fishing zone using chlorophyll, SST and wind speed and land based geophysical parameters. The Primary satellite (EOS-06) has been separated in Orbit-1. The satellite launch was witnessed by Secretary, MOES Dr. M. Ravichandran and Secretary, DBT Dr. Rajesh Gokhale.
Subsequently Orbit was changed by using two Orbit Change Thrusters (OCTs) introduced in the Propulsion Bay Ring of the PSLV-C54 Vehicle. Later all the seven commercial satellites from NSIL were deployed successfully.
Astrocast is a 3U spacecraft with 4 nos. of Satellites from Spaceflight Inc, USA, were separated subsequently.
The Thybolt is a 0.5U spacecraft bus that includes a communication payload to enable rapid technology demonstration and constellation development for multiple users from Dhruva Space using their own Orbital Deployer with a minimum lifetime of 1 year, was deployed in the intended orbit.
The Anand three axis stabilized Nano satellite is a technology demonstrator for miniaturized electro-optical payload and all other sub-systems like TTC, power, onboard computer and ADCS from Pixxel, India was also placed in the orbit successfully
INDIA-BHUTAN SAT a collaborative mission between India and Bhutan is INS-2B satellite for Bhutan with two payloadsviz. NanoMx, a multispectral optical imaging payload developed by Space Applications Centre (SAC) and APRS-Digipeater which is jointly developed by DITT-Bhutan and URSC was successfully deployed.
Sri S Somanath, Secretary, Department of Space / Chairman, ISRO explained the launch as a perfect text book launch and he congratulated the ISRO team, NSIL, Industry, customer for the fabulous achievement.
Later External Affairs Minister Dr. S Jaishankar addressed the nation and applauded the efforts put in by ISRO and Bhutan scientists for this mission which will mark the extended co-operation in space between the two countries under the leadership of Hon’ble Prime Minister Shri Narendra Modi. He also recalled the inauguration of ground earth station established by ISRO for the south Asea satellite, jointly by both the countries, during the visit of Hon’ble Prime Minister Sri Narendra Modi during 2019.
Minister of Information and Communications, Royal Government of Bhutan addressed the community and expressed his full satisfaction with the launch and effort taken by ISRO and Bhutan teams.
All the users from Dhruva Aerospace, Pixxel India were present in the launch.
Some of the major sub-systems of the satellite were supplied by Indian Industry viz. Ananth Technologies, Newtech, Centum, Cosmos, DataPatterns, HAL , PARAS Defence limited.
The live launch was witnessed by 10342 people from the open view gallery at SDSC SHAR, Sriharikota.
26-Nov-2022: The third generation Indian satellite for monitoring the oceans, formally named as Earth Observation Satellite-6 (EOS-6) was launched today by the Indian Space Research Organization (ISRO) in partnership with Ministry of Earth Sciences
The third generation Indian satellite for monitoring the oceans, formally named as Earth Observation Satellite-6 (EOS-6) was launched today by the Indian Space Research Organization (ISRO) in partnership with Ministry of Earth Sciences (MoES) among others, from its First Launch Pad (FLP) at Satish Dhawan Space Centre (SDSC), Sriharikota.
The ocean observing mission is a follow up to OceanSat-1 or IRS-P4 and OceanSat-2 launched in 1999 and 2009, respectively. The satellite was launched aboard the proven launch vehicle PSLV (Polar Satellite Launch Vehicle) on its 56th flight (24th flight of the PSLV-XL version). Today’s launch, designed as PSLV-C54, also accommodated other small satellites along with Oceansat-3.
The Oceansat-3 was placed in the polar orbit at the height of about 740 kilometers above sea level. While at ~1100 kilograms, it is only slightly heavier than Oceansat-1, for the first time in this series it houses three ocean observing sensors viz Ocean Color Monitor (OCM-3), Sea Surface Temperature Monitor (SSTM), and Ku-Band scatterometer (SCAT-3). There is also an ARGOS payload. All these sensors have their own importance for India’s blue economy aspirations.
The advance 13 channel OCM with 360 m spatial resolution and 1400 km swath will observe the day side of the earth every day and will provide crucial data on distribution of ocean algae which is the base of the food chain within marine ecosystem. The OCM-3 with high signal-to-noise ratio is expected to provide improved accuracy in daily monitoring of phytoplankton having wide range of operational and research applications including fishery resource management, ocean carbon uptake, harmful algal bloom alerts, and climate studies.
The SSTM will provide ocean surface temperature which is a critical ocean parameter to provide various forecasts ranging from fish aggregation to cyclone genesis and movement. Temperature is a key parameter required to monitor health of the coral reefs, and if needed, to provide coral bleaching alerts. The Ku-Band Pencil beam scatterometer onboard EOS-6 will provide high resolution wind vector (speed and direction) at the ocean surface, something which any seafarer would like to know of, whether its fishermen or shipping company. The data of temperature and wind is also very important for assimilation into ocean and weather models to improve their forecast accuracies. ARGOS is a communication payload jointly developed with France and it is used for low-power (energy-efficient) communications including marine robotic floats (Argo floats), fish-tags, drifters, and distress alert devices useful for conducting effective search and rescue operations.
Union Minister of State (Independent Charge) Science & Technology; Minister of State (Independent Charge) Earth Sciences; MoS PMO, Personnel, Public Grievances, Pensions, Atomic Energy and Space, Dr Jitendra Singh in a message from Jammu congratulated and thanked ISRO and MoES teams for successful launch.
The Minister said, while ISRO will continue to maintain the orbit of the satellite and its standard procedures for data reception, archive etc the major operational user of this satellite would be MoES institutions viz Indian National Centre for Ocean Information Services (INCOIS), Hyderabad and National Centre for Medium Range Weather Forecasting (NCMRWF), Noida that provide a bouquet of services every day for lakhs of stakeholders across the nation.
Dr Jitendra Singh noted that for this purpose, INCOIS has also established a state-of-the-art satellite data reception ground station within its campus with the technical support of National Remote Sensing Centre (ISRO-NRSC), Hyderabad. He also asserted that ocean observations such as this will serve as strong foundation for the India’s blue economy and polar region policies.
Dr. M. Ravichandran, Secretary, MoES, in congratulatory note to ISRO said, the launch of Oceansat-3 today is also significant since this is the first major ocean satellite launch coming from India since the initiation of the UN Decade of Ocean Science for Sustainable Development (UNDOSSD, 2021-2030). He said, this satellite will have the capability to make concurrent measurements of Ocean Colour, SST and Sea Surface Winds, and is expected to provide a great boost to the ocean observing capabilities of the global scientific and operational communities in addressing the Ocean Decade objectives and challenges.