At a height of 1.5 million km, the James Webb Telescope uses frequencies similar to satellite internet services to transmit data back to Earth.
On July 12, the National Aeronautics and Space Administration (NASA) shared the first series of color images from the James Webb Telescope. Posted on the NASA website in JPEG format, these images have undergone multiple processing stages, with the original data not being photos.
Like other scientific instruments, the James Webb collects observational results and sends them back to Earth in raw data format. Some of the observational systems equipped on the telescope include the Near Infrared Camera (NIRCam), Mid-Infrared Instrument (MIRI), spectrometers, light-blocking devices from stars, and several other instruments.
This is how the James Webb transmits data from a distance of 1.5 million km to Earth, enabling scientists to produce the clearest cosmic images ever captured.
A 123 MP Resolution Image
One of the images released on July 12 by the James Webb captures the NGC 3324 galaxy cluster within the Carina Nebula. The Hubble Space Telescope photographed a similar image in 2008. When placed side by side, the James Webb’s image displays significantly higher detail and clarity.
In the new image, the structure of the nebula is clearly depicted, along with the appearance of small stars, which can be seen even when the image is enlarged. The color representation from both telescopes also differs.
Image of the NGC 3324 galaxy cluster from the Hubble Telescope (top) and the James Webb. (Photo: NASA).
The reason the James Webb’s images show so much detail is due to the amount of data collected and the higher original resolution of the images. According to TechCrunch, the original images (created after processing the raw data) from the James Webb have a resolution of 123 MP and a size of 137 MB. In contrast, Hubble’s images have a resolution of 23.5 MP and a size of 32 MB.
Theoretically, images from the James Webb contain five times more detail compared to Hubble. However, in reality, the James Webb is much more powerful with data transmission potentially 25 times greater, from a distance over 3,000 times farther than Hubble.
Data Transmission Speed Comparable to the Internet
Launched in 1990, the Hubble Telescope orbits at a low Earth orbit, approximately 547 km above the surface. This altitude is lower than that of GPS satellites, which are launched into medium orbits (about 20,000 km). Therefore, communication with Hubble from Earth is relatively straightforward.
In contrast, James Webb is positioned at the second Lagrange point (L2), approximately 1.5 million km from Earth. This location is a balance point of the gravitational forces of the Earth and the Sun. The altitude of the James Webb compared to Earth is four times the distance from Earth to the Moon.
Illustration of the distance between James Webb and the Hubble Telescope. (Photo: NASA).
However, Earth-based systems have previously transmitted data over much greater distances. Currently, the longest recorded communication between Earth and the Voyager 1 spacecraft occurred in January at a distance of nearly 23.3 billion km.
With James Webb, NASA engineers can accurately track the spacecraft’s position in real-time. Therefore, they simply need to select the appropriate tools to ensure smooth communication.
To communicate with Earth, James Webb uses Ka-band radio waves, within the 25.9 GHz range. This is also the frequency used by telecommunications and internet satellites, including Starlink. As a result, James Webb can transmit data at speeds comparable to internet speeds, around 28 Mbps. Thus, James Webb has the capability to send 57 GB of data back to Earth each day.
James Webb is also equipped with another antenna that uses the S-band with frequencies between 2-4 GHz. This band is also used for Wi-Fi and Bluetooth connections.
Due to the continuous rotation of the Earth, signals can be obstructed by lower objects. To mitigate this, NASA has scheduled data transmission months in advance through the Deep Space Network.
James Webb Mission Control Center. (Photo: NASA).
The SSD of James Webb has a capacity of about 68 GB, built from special materials to withstand the altitude of over 1.6 million km. Depending on operational schedules, the hard drive will fill up in at least 120 minutes to one day. Data is transmitted back to Earth and stored on NASA servers before being deleted from the James Webb. For comparison, the Hubble Telescope can only store 2 GB of data.
How Images are Created from Data
“A telescope is not an instant camera… It is a scientific tool designed to produce scientific results,” said Joseph DePasquale, head of the image processing department for James Webb at the Space Telescope Science Institute.
Even when sent back to Earth, some of James Webb’s data cannot be read immediately. The raw data collected by James Webb using infrared light sensors falls outside the visible spectrum for humans.
“Essentially, it looks like a black image with some white spots due to the very large sensitivity range… We have to go through a process called data stretching, taking some pixel values and rearranging them so you can see every detail that’s there,” DePasquale explained.
To “color” the images, the research team mapped the wavelengths of the infrared light recorded by the telescope in monochrome into three colors: red, blue, and green. By combining the three images with brightness representing each color, DePasquale’s team produced a complete color image.
Atmospheric composition chart of the gas planet WASP-96b recorded by James Webb. (Photo: NASA).
Taking the image of the NGC 3324 galaxy cluster as an example, even though they depict the same location, the various optical devices with different infrared data collection capabilities result in differing colors after processing.
In addition to visually representable data, James Webb also brings back many other crucial pieces of information, such as spectral charts showing detailed components in the atmosphere of a planet.
With its modern tools, scientists hope that James Webb will provide detailed data to enhance our understanding of the origins of the universe, uncover clues about human formation and existence, as well as the potential for life beyond Earth. In addition to serving the field of astronomy, the public eagerly awaits the next images created from the data of this telescope.
