Spitzer Space Telescope

The Telescope was named after an American theoretical physicist and Astronomer Lyman Spitzer. It was launched aboard Delta II rocket in August 2003, with a mission period of 30 months. After completely exhausting the cooling system required for full operational capability in May 2005, most of the equipment was declared unusable and shut down. But some of the scientific equipment continued working until January 2020. 

Spitzer Specifications

Total Weight (At launch)	950 kg (2094 lbs)
Helium mass	50.4 kg (111 lbs)
Nitrogen Propellant	15.6 kg (34.4 lbs)
Diameter	85 cm (2.79 feet)
Imaging Photometry	3-180 Microns
Spectroscopy	5-40 Microns
Spectrophotometry	50-100 Microns
Planetary Tracking	1 arcsec/sec
Liquid Helium volume	360 liters (95 Gallons)
Diffraction limit	1.5 arcsec at 6.5 Microns
Orbit	Heliocentric

What does it sense?

Any object in space having a temperature above 0 Kelvin (-273.15 degrees Celcius) emits infrared radiation. Human eyes are not able to see these radiations, but we can feel it as heat. The Spitzer was specifically designed to observe the infrared light emitted by Galaxies, Exoplanets, and Stars deep into space. To avoid interference between its own body temperature and its observations, the telescope, and its detectors were cooled down to a temperature of 5 kelvin (-268 degrees Celsius).

Spitzer's Structure

As contradictory as it may sound, The Spitzer needed to be at room temperature as well as at -268 degrees Celsius simultaneously for the reason mention above. And hence the Spitzer’s structure was separated into 2 different components. 

1. Cryogenic Telescope Assembly(CTA)

2. The Spacecraft

The CTA was attached to spacecraft using special insulating struts and a number of thermal radiation shields to prevent heat from spacecraft to reach to the Telescope. 

Cryogenic Telescope Assembly consisted of the Telescope, Cryostat, Outer Shell Group, and Multiple Instrument Chamber which included Infrared array camera, Infrared Spectrograph, and Multiband imaging photometer. Liquid Helium in the Cryostat tank acted as a coolant that produced freezing vapor to cool the CTA down to -268 degrees Celsius. The outer shell was made from aluminum. It was shiny to the side facing the Sun and was painted black on the side facing away from the Sun in order to reflect the Sunlight and radiate heat as much as possible. 

The Spacecraft consisted of 2 parts, Solar Panels, and Spacecraft Bus. Solar Panels were used to generate electrical power for the instruments on the spacecraft and also to shield the telescope for the Sun. Spacecraft Bus was an octagonal structure consisting of data handling units, reaction control subsystem, telecommunication subsystem, power generation, and distribution subsystem, flight software. These instruments performed engineering functions such as Communication with ground control here on Earth, Telescope Stabilization, and Orientation in the desired direction, providing electrical power to science instruments.

Science Instruments

Infrared Spectrograph: Each element in the Universe has its own unique light signature. IRS breaks the incoming Infrared light into different spectrum and allows astronomers to detect what the object is made up of. IRS has 4 modules with a separate entry slit on each to allow infrared light to enter into spetrograph.

1. Low-resolution, Short-wavelength module with Detecting Range 5.3 - 14 microns
2. Low-resolution, Long-wavelength module with Detecting Range 14 - 40 microns
3. High-resolution, Short-wavelength module with Detecting Range 10 - 19.5 microns (High Details)
4. High-resolution, Long wavelength module with Detecting Range 19 - 37 microns (High Details)

Infrared Array Camera: Imaging camera customized specifically for wavelengths from 3.6 to 8.0 microns. It has 4 different detectors which simultaneously takes image of 3.6, 4.5, 5.8, 8.0 microns of wavelength. Camera shutter is the only moving part on the entire IARC instrument. 3.6, 4.5 micron detectors are made from indium and antimony while 5.8, 8.0 micron wavelength detectors are treated with arsenic. 

Multiband Imaging Photometer: Imaging camera customized for far Infra-red wavelengths: 24, 70 and 126 microns. 24 micron detector is made up of silicon and specifically treated with arsenic. 70 and 160 micron arrays are made of germanium treated with gallium. Scan mirror is the only moving part of the MIPS which is used for mapping large areas of the skies.