Understanding Spectrometers (MAESTRO)

There are two spectrometers onboard SCISAT-1, the first belongs to the Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) experiment. The task of the MAESTRO spectrometer is to record the spectrum of the sun before and after sunlight has passed through the Earth's atmosphere.

Analysis of the spectra will give the MAESTRO scientific team information about various processes involved in the chemical and physical dynamics of the Earth's atmosphere, especially about the opacity of aerosols in the atmosphere and how they affect the atmosphere's energy balance.

Transparency Master

A spectrometer is really a very simple device which has extraordinarily powerful applications.

Basically it consists of three parts

  1. A small telescope which collects light from a luminous source. The light is focused into a thin beam using a narrow slit and a set of specially designed lenses.
  2. A diffraction grating (which acts like like a prism) to produce a spectrum from the incident beam of light.
  3. A detector, such as a photocell, to measure the intensity of the light in various regions of the spectrum. A simple voltmeter and a photocell can be used as a detector system.

Transparency Master

To record the spectrum the voltmeter can be replaced by a chart recorder. As the detector "scans" across the spectrum, the intensity of the light at each point can be recorded.

The detector can also be attached to a computer interface. This allows the computer to record the light intensity, this data can be stored, transmitted and printed as a graph for analysis.

The spectrum can be scanned by either moving the detector or, more commonly, by rotating the grating.

Intensity vs. Wavelenght
Transparency Master

The scanned result usually looks similar to the chart shown above.

Every source of light has a unique spectrum. From analysis of the spectrum one can determine such things as the temperature, chemical composition and motion of the source.

The x-axis plots the wavelength and the y-axis plots the intensity of the light at each wavelength in the spectrum.

Student Assignment