Imagine shining a laser beam at a penny 200 miles away. Now imagine doing that for twenty-four hours straight while riding a carousel. Sound difficult? That's exactly what the Hubble Space Telescope does.
After months of technical problems, NASA announced on June 4 that Hubble had entered the Single gyroscope modeThis essentially signifies that the telescope has to depend on just certainly one of the several gyroscopes – devices that measure the orientation of an object in space – that it normally uses to trace objects in space.
Named after the astronomer Edwin HubbleThe Hubble telescope was launched into low Earth orbit in 1990. Here it sits above the Earth's atmosphere, which interferes with observations from ground-based telescopes. During its three many years of use, it has provided us with stunning images of distant galaxies and allowed scientists to look closer to the start of the universe.
Hubble takes clear, high-resolution images of stars billions of sunshine years away. To get enough Photons – light particles – To produce a high-quality image, it essentially acts as a really low-speed camera, keeping its aperture – the opening within the lens that lets light through – open for as much as 24 hours to capture a single image.
Anyone who has ever taken a photograph with a slow shutter speed knows how difficult it’s to avoid a blurry image. Hubble takes this to the acute. It has to remain pointed at the identical distant point in space. with an accuracy inside just a few milliarcseconds – where a milliarcsecond is 3,600,000th of a level – for as much as 24 hours. And the satellite must maintain this accuracy while orbiting the Earth at 27,000 kilometers per hour through extreme heat and cold.
To keep its sights on its goal and produce clear images, Hubble uses what aerospace engineers like me call attitude control systems. All spacecraft and aircraft have an attitude control system that helps them steer in the appropriate direction.
What is a gyro anyway?
An attitude control system consists of a series of sensors measuring the orientation of the spacecraft, a series of actuators – thrusters, response wheels or control torque gyros – that move the spacecraft, and a flight computer. The flight computer takes the measurements from the sensors and generates the commands for the actuators.
NASA/STSci
A gyroscope is a tool that measures the position or orientation of an object in space. In other words, it measures how far the item has rotated from a set point. In order for Hubble to know where to point to take an image, it must know where it’s in space. It needs not less than three gyros – one per axis.
Hubble originally had six gyros: three principal and three auxiliary gyros. But after greater than 30 years in orbit 4 of the gyros have failed from age-related complications.
Of the 2 remaining gyroscopes, NASA has reserved one as a substitute, so Hubble is now Operation with a single gyroBut for those who need not less than three gyros – one per axis – to know where you might be, how can Hubble determine its location with only one gyro?
The clever answer from NASA engineers is definitely quite easy: the missing gyroscopes may be replaced by other sensors on the telescope, similar to magnetometers and star sensors.
Gyro substitute
Magnetometers measure the Earth’s local magnetic fieldscientists understand quite well. They can Use the magnetometers to get a rough idea of location in relation to the known magnetic field direction, much the identical way you employ a compass. A 3-axis magnetometer can measure the strength and direction of the Earth's magnetic field because the satellite moves along its orbit to find out its orientation in space.
Or you should utilize Star Tracker or solar sensors, that are far more accurate than magnetometers. These sensors Use a map of the sky and line up what you see with what's on the map to determine where you're pointing.
By combining star trackers, solar sensors, magnetometers and a single gyroscope, Hubble can achieve a targeting accuracy that could be very near the three-gyroscope configuration – although the single-gyroscope configuration limited how briskly Hubble can track objects in space.
Hubble has probably the most precise attitude control systems ever built and has given people stunning images of the early universe. But the lack of all but two of its gyros is just one other indication that Hubble's days are numbered.
Hubble's successor, the James Webb Space Telescope, launched on December 25, 2021. It is stationed 1,000,000 miles (1,609,344 km) from Earth within the so-called second Lagrange point (L2).
At this point, the telescope, the Earth and the Sun are at all times aligned, and the telescope's sunshade blocks the sun's rays. This feature allows its infrared camera to work at cooler temperatures and thus deliver significantly higher image quality.
While the discoveries of the Hubble telescope paved the best way for astronomers to explore the universe, the discoveries of the Webb telescope will give us deeper insights into the cosmos than ever before.
image credit : theconversation.com