In our previous article we got a glimpse of: what is Hubble Telescope and why it is needed? In our second and last part of this series, we will explore its working and various facts related to it.
Hubble is a Cassegrain reflector telescope. Light from celestial objects travels down a tube, is collected by a bowl-like, inwardly curved primary mirror and reflected toward a smaller, dome-shaped, outwardly curved secondary mirror. The secondary mirror bounces the light back to the primary mirror and through a hole in its center. The light is focused on a small area called the focal plane, where it is picked up by its various science instruments (Figure 1).
Hubble’s science instruments, the astronomer’s eyes to the universe, work together or individually to provide the observations. Each instrument is designed to examine the universe in a different way. Hubble holds two main varieties of instruments: cameras, which capture Hubble’s famed images, and spectrographs, which break light into colors for analysis.
Hubble’s current suite of instruments includes:
- Wide Field Camera 3 (WFC3)
- Cosmic Origins Spectrograph (COS)
- Advanced Camera for Surveys (ACS)
- Space Telescope Imaging Spectrograph (STIS), and
- Fine Guidance Sensors (FGS).
The various key components of Hubble Telescope and its importance is as follows:
- Spacecraft systems: Hubble is operated by commands from the ground. Several spacecraft systems are in place to keep Hubble functioning smoothly.
- Communications antennas: The antennas allow technicians to communicate with the telescope, telling it what to do and when to do it. Four antennas receive and send information to a set of satellites, which in turn communicate with Earth.
- Solar arrays: Each wing-like array has solar cells that convert the Sun’s energy into electricity. Some of that electricity runs the telescope, some is stored in onboard batteries for the periods when Hubble is in Earth’s shadow.
- Computers and automation: There are two main computers. One talks to the instruments, sends commands and other information, and transmits data; the other handles pointing control, gyroscopes and other system-wide functions.
- Thermal protection: Hubble has blanket of multilayered insulation, which protects the telescope from temperature extremes.
- Pointing system: Hubble uses a combination of gyroscopes, reaction wheels and Fine Guidance Sensors to orient itself.