Located 80 km from Pune, the GMRT is an array of 30 parabolic dishes — each of which is 45 metres in diameter.
An erroneous allocation of airwaves in restricted frequency bands to telecom provider Reliance Jio Infocomm Limited (RJIL) is threatening the quality of scientific research at the Giant Metrewave Radio Telescope (GMRT), the world’s largest radio telescope operating at metre wavelengths, according to scientists involved in research at the facility.
Located 80 km from Pune, the GMRT is an array of 30 parabolic dishes — each of which is 45 metres in diameter. These dishes are arranged in an ‘Y’ fashion across a 30 km region near Narayangaon. The site, situated off the Pune-Nashik highway, was chosen in the early 1980s as it had barely any man-made noise and was favourable for long-term telescope operations.
A project of the Department of Atomic Energy (DAE) under the Tata Institute of Fundamental Research (TIFR), the GMRT is a unique facility functioning within the frequency bandwidth of 100 MHz – 1500 MegaHertz (MHz). Built and operated by the TIFR-National Centre for Radio Astrophysics (NCRA), Pune, it is a highly sought after telescope, with the number of users seeking telescope observation time often exceeding the availability.
GMRT enjoys special protection for carrying out exclusive operations around a spectrum of 900 MHz for its astronomical pursuits. The telescope operates for anywhere between nine to 10 months in a year and remains shut for maintenance in the remaining months.
To carry out scientific quests, the GMRT makes use of highly-sensitive specialised receivers installed on each of its 30 antennas that capture extremely faint radio signals coming from the farthest corners of our Universe.
Even the slightest interference in this process can result in signal loss, thus defeating the purpose of setting up such a sensitive telescope operating in this part of the radio spectrum.
However, the Department of Telecommunication’s (DoT’s) “unchecked spectrum allocation” to RJIL has caused severe deterioration in the data quality produced by this world-class telescope, and has posed hurdles for the Indian and global scientific user community from over 30 countries. This mistake has also led to wastage of GMRT funds and is affecting its scientific reputation.
The DoT had erroneously allocated RJIL a spectrum between 800 MHz and 900 Mhz, coinciding with that of the GMRT’s operations.
“Though Reliance was operating in the region even earlier, significant signal interference was noticed only in 2016-2017. That was when NCRA first contacted and informed RJIL about the matter in 2017,” a leading scientist from NCRA told The Indian Express.
When contacted via email and phone on this matter, RJIL’s western region office, which is in charge of its operations in Maharashtra, declined to comment.
In 2018, the telescope underwent its first major upgrade, (it is now known as uGMRT), becoming more sensitive and possessing a capability to look deeper into the unexplored areas of the Universe. With an improved computational capacity of up to 10 Teraflops and an ability to perform data transfer of up to 40 GB/sec, the uGMRT today produces useful scientific data to the tune of several Terabytes/day.
But due to strong signal interferences generated by the operations of Reliance Jio in the region, NCRA officials said that large datasets have been permanently damaged. Scientists have also been forced to abandon certain observations using uGMRT due to such disturbances.
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As the issue remained unresolved, the NCRA formally took up the matter with the DoT in early 2018. Subsequently, during some meetings between representatives of NCRA, DoT and telecom operators (including RJIL representatives), NCRA requested the ministry to allocate an alternate spectrum at higher frequencies, outside the 800 – 900 MHz range, to RJIL. It also brought to the ministry’s notice that GMRT enjoys a de-facto protection from all kinds of radio interference, at around 900 MHz, from the vicinity.
Even though the DoT assured them of a positive solution three years ago, the ministry is yet to arrive at a final decision, thus threatening the scientific goals of uGMRT as RJIL continues its operations.
NCRA scientists said they have followed up with the DoT about this issue multiple times since 2018, but the ministry’s “inaction and delay” in reallocating a suitable spectrum to RJIL has now begun to hamper uGMRT’s data quality beyond repair.
Human-induced interferences have been a matter of serious concern for multi-million dollar telescopes operating across the world. But the scientific community has always managed to work around and find solutions for it. This has resulted in the coexistence of all stakeholders alongside preserving various scientific interests.
This holds true even with GMRT, as all telecom companies, police wireless services, Air Traffic Control and other sources in the locality have been coordinating with the GMRT to help reduce the interference effects as much as possible.
The NCRA has encouraged telecom companies to operate at frequencies around 1800 MHz, which is not used by the GMRT, the officials said.
“But due to the continuing operations of RJIL within GMRT’s spectrum in the region, the quality of data — also shared with the international astronomy community – is getting compromised. We urge DoT to intervene at the earliest and protect GMRT from suffering further data quality losses,” added a scientist who is a frequent user of the GMRT.
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