Voyager 1 Imaging Science Subsystem final draft #2

February 16, 2024

Voyager 1 Imaging Science Subsystem final draft #2

The Imaging Science Subsystem (ISS) of Voyager 1 was used to capture valuable scientific images of the Jupiter and Saturn system allowing valuable research insights before adventuring into deep space (JetPropulsionLab, n.d.). Voyager 1 played a crucial role in exploring the Jupiter system and paved the way for further deep space exploration around the Jovian systems. In terms of features, the system consists of two cameras, a 1500mm high-resolution narrow-angle f/8.5 camera and a 200mm lower resolution wide angle f/3 camera. (SETI, n.d.) As mentioned in the related webpage the high-resolution cameras allow scientific data collection such as atmospheric composition and coloured imagery of the planets. The operations of the cameras are controlled by a spacecraft computer which communicates with Earth’s computer systems (NASA, n.d.).

Being launched in 1977, the spacecraft had the most technologically advanced in its imaging system at the time. However, the modern spacecraft imaging system of the James Web Telescope has improved based on the Voyager 1 imaging system and brings advantages for scientists to further study other planets with the images captured.

According to NASA, n.d., Voyager 1 cameras are both mounted in front of the vidicons with 8 filters in a commendable Filter Wheel. Both low-resolution wide-angle and high-resolution narrow-angle are television-type cameras. The images of the planetary atmosphere captured by the cameras help data analysts determine the wind velocities of each region observed (NASA, n.d). The imaging science subsystem helps to search for new rings by “map the radial and azimuthal distribution of material in the ring plane”. It attains comprehensive multi-spectral imaging across all satellites, determines rotation speeds and spin axis orientations, examines Triton's surface features at resolutions below 2 km, and explores for any unidentified moons (NASA, n.d).

The Voyager Imaging Science Subsystem employed a magnetic deflection vidicon with a 25mm diameter, utilising a selenium sulphur target capable of retaining high-resolution images over 100 seconds. The active imaging area measures 11.14 x 11.14 mm, and each frame consists of 800 lines with 800 pixels per line. The electronic readout of one frame takes 48 seconds. Light flooding is used to remove residual images, followed by 14 erase frames to stabilise the vidicon target for the next exposure sequences. (VGR ISS Calibration Report, 1978)

Compared to the James Web Telescope launched in 2021, Voyager 1’s imaging system seems classic and simpler. James Web Telescope has a near-infrared camera (NIRCam) detector with optical baffles removed (NASA, n.d.). There are 2 different types of detectors: mercury-cadmium-telluride “H2RG” detector and arsenic-doped silicon detector. The “H2RG” detector is for 0.6-5 micrometres “near infrared” while the other one has 5-28 micrometres for “mid-infrared” and has about 4 million pixels and 1 million pixels (NASA, n.d.).

According to NASA, the mercury-cadmium-telluride can be tuned to sense longer or shorter wavelengths by varying the ratio of mercury to cadmium. This feature can help to tailor each camera detector and obtain the peak performance over the wavelength which will be used (NASA, n.d.). The other feature is MIRI, an instrument specialising in mid-infrared detection, which operates under the coldest temperatures among all the telescope’s instruments (Space.com, n.d.). MIRI required additional cryocoolers to reach a temperature of -266 degrees, which is only 7 degrees above absolute zero, where atomic motion ceases (Space.com, n.d.).

In conclusion, the Imaging Science Subsystem of Voyager 1 plays a pivotal role in capturing valuable scientific images of the Jupiter and Saturn systems, providing valuable insight before venturing into deep space. As the most technically advanced spacecraft in 1977, Voyager 1 served as the foundation of subsequent space exploration spacecraft. However, the modern James Webb Space Telescope launched in 21, surpassed the Voyager 1’s imaging capabilities with new technology like near-infrared detectors with adjustable wavelengths tailored camera detector and specialised instrument operating at extremely cold temperatures. While Voyager 1’s imaging system appear classic and simpler, it is the foundation of that enhanced our ability to study and understand the space better with technology advancement.