Space: NASA turns on James Webb Space Telescope’s high-gain antenna
NASA has turned on the high-gain antenna on the James Webb Space Telescope, allowing the $10 billion observatory to send images and data back to Earth.
James Webb — the most complex space telescope ever built — was launched in late December last year and is intended as the successor to the Hubble observatory.
Among the telescope’s goals will be surveying potentially habitable exoplanets and some of the most distant and oldest objects in the observable universe.
Until now, communications with the telescope had all been via its medium-gain antenna, using the microwave ‘S-band’ of frequencies between 2–4 GHz.
The high-gain antenna, which operates instead in the ‘Ka-band’ (26.5–40 GHz), will allow a higher downlink rate via NASA’s Deep Space Network, the agency said.
This network sports three ground stations — in California, Canberra and Madrid — meaning that one location will also be visible to Webb as the Earth turns.
The Ka-band has three data transfer speeds to select from, with the default being the highest, which operates at 3.5 megabytes per second.
For comparison, the average download speed on a 4G mobile phone connection is around 1–1.25 megabytes per second.
The two slower speeds, meanwhile, can be used to compensate for bad weather at the ground station that might produce interference.
When the telescope begins observations in mid-summer this year the high-gain antenna will transfer at least 28.6 Gigabytes of science data to Earth twice daily.
Scroll down for video
NASA has turned on the high-gain antenna on the James Webb Space Telescope (pictured), allowing the $10 billion observatory to send images and data back to Earth
Until now, communications with the telescope had all been via its medium-gain antenna, using the microwave ‘S-band’ of frequencies between 2–4 GHz. The high-gain antenna, which operates instead in the ‘Ka-band’ (26.5–40 GHz), will allow a higher downlink rate via NASA’s Deep Space Network, the agency said. Pictured: the antenna assembly on the spacecraft bus
The Deep Space Network sports three ground stations — in California, Canberra and Madrid — meaning that one location will also be visible to Webb as the Earth turns. Pictured: the 70 m antenna at the Goldstone Deep Space Communications Complex, California
James Webb (depicted) — the most complex space telescope ever built — was launched in late December last year and is intended as the successor to the Hubble observatory
The high-gain dish — part of the James Webb’s gimbaled antenna assembly — was released back on 26 December, one day after launch, but well before the craft’s arrival last week at the gravitationally stable ‘Lagrange point’ where it has since ‘parked’.
The antenna assembly is located on the ‘underside’ of the telescope, being attached to the spacecraft bus which houses the telescope’s power, altitude control and communications systems.
‘It has been about a month since launch, and it has been an unbelievable ride. I am so filled with pride for our team,’ said James Webb Space Telescope project manager project manager and engineer Bill Ochs, of NASA’s Goddard Space Flight Center.
‘The perfection of the deployment execution and the subsequent activities reflects directly on how hard everyone worked and the diligence and sacrifice it took on the part so many people.’
‘We are now ready to align mirrors and commission instruments and have already proven that all the hardware associated with the optics (including 132 actuators) is working beautifully.’
‘By the time we get to instrument commissioning, we are going to have one hell of a telescope,’ he continued.
‘Finally, our ops team and ground system have done a fantastic job of executing the commissioning timeline, and all those rehearsals have paid off.’
As Mr Ochs noted, the next step in getting the James Webb Space Telescope ready for scientific observations is to align each of the 18 primary mirror segments to ensure the telescope produces sharp, focused images.
To do this, NASA will be pointing the telescope at HD 84406 — a sun-like, type G star that lies some 260 light-years-away in the constellation of Ursa Major.
While this star is really too bright for James Webb to study properly, it is perfect for aligning its mirrors.
Among the telescope’s goals will be surveying potentially habitable exoplanets and some of the most distant and oldest objects in the observable universe
The next step in getting the James Webb Space Telescope ready for scientific observations is to align each of the 18 primary mirror segments to ensure the telescope produces sharp, focused images. Depicted: the size of James Webb’s primary mirrors vs that of Hubble
Engineers will take 18 separate, out-of-focus images of HD 84406 using each of the mirrors, from which a computer will determine exactly how each must be oriented to bring the telescope into focus.
Each mirror’s direction can be adjusted in the very tiniest of increments — each equal to a ten-thousandth of the width of a human hair.
According to NASA, the initial alignment process is expected to take several months to complete. When the telescope is up and running, the mirrors will also need to be checked and, if necessary, realigned every few days.
To align James Webb’s mirrors, NASA will be pointing the telescope at HD 84406 — a sun-like, type G star that lies some 260 light-years-away in the constellation of Ursa Major. Engineers will take 18 separate, out-of-focus images of HD 84406 using each of the mirrors, from which a computer will determine exactly how each must be oriented to bring the telescope into focus