Lecture 5

Question 1

When and who did the first infrared observations?

Answer 1

William Herschel 1801

Question 2

What are the two types of IR detectors?

Answer 2

Thermal and photonic

Question 3

How does a thermal IR detector work?

Answer 3

They record the change in properties (Resistance[Bolometers], voltage[Thermocouples/Thermopiles] or crystals[pyroelectric detectors]) as the temperature of the detector changes

Question 4

How does a photonic IR detector work?

Answer 4

Photonic detectors react to the impact of photons which cause electronic excitations. These are faster and more sensitive (Than the thermal detectors) but have to be cooled much more

Question 5

What was the IRAS? (InfraRed Astronomical Satellite)

Answer 5

• First ever Space based observatory working in Infra red
• Made a survey of entire sky at IR wavelengths
• Launched 25 January, 1983 – Mission lasted 10 months
  Discovered 350K new sources

Question 6

What was the ISO? (Infrared space observatory) What were the instruments on the ISO?

Answer 6

The ‘first’ IR space observatory, since IRAS did the first mapping. ISO made particularly important studies of the dusty regions of the Universe, where visible light telescopes can see nothing.

ISOCAM: A camera with a low-resolution spectrograph
ISOPHOT: A multichannel photometer
SWS: A spectrometer for the shorter wavelengths
LWS: A spectrometer for the shorter wavelengths

Question 7

What was SPITZER and what did SPITZER do?

Answer 7

A space telescope (85cm) operating in the IR spectrum. It was the third launched space telescope operating in IR (since ISO and IRAS).

Question 8

What were the instruments of SPITZER?

Answer 8

IRAC - InfraRed Array Camera

IRS - InfraRed Spectrometer

MIPS - Multiband Imaging Photometer for Spitzer.

Question 9

What is meant by Warm SPITZER?

Answer 9

SPITZER was cooled by Liquid He to 5.5K. After the helium was exhausted, the s/c have stabilized at 30K.

This allows IRAC to operate with its two shortest wavelengths (3.6 µm, 4.5 µm). Among programs are further observations of exoplanets.

Question 10

What was Herschel?

Answer 10

A large space-based infrared telescope which bridged the far infrared and sub-millimetre to study the ‘cool’ universe. (Active 2009-2013)

Question 11

What were the instruments of Herschel?

Answer 11

PACS - Photodetector Array Camera and Spectrometer

SPIRE - Spectral and Photometric Imaging Receiver

HIFI - Heterodyne Instrument for the Far Infrared