The instrument is composed of three spectrometers that together cover the wavelength domain extending from 165 nm to 3100 nm. Each spectrometer is a double monochromator using concave holographic gratings to reduce scattered light. The gratings are mounted on a common mechanical shaft which rotates by steps and is driven by a nut-screw system.
Between each exit slit and detector, a wheel carrying second order filters and appropriate attenuators permits the reduction of the incident flux to keep the number of counts in an acceptable range for the detectors. The three wheels are positioned as a function of wavelength to take into account the change in solar irradiance and the variation of the spectrometer's responsivity with wavelength in particular at both ends of each spectrometer wavelength domain.
The mechanical structure is composed mainly of:
-a centre plate (5 kg) equipped of 6 attachment feet where are fixed the optical and electrical units
-2 covers (top & bottom)
The electronic items are :
-Low and high voltages DC/DC converters
-Lamps Power Suppy
-Stepper Motors Power units
-Houskeeping units
-CPU including the flight software
-IR Synchronous Detection
Optics items are
-3 Spectrometers
-3 Detectors
-1 Position Sensitive Detector
-Mirrors
-1 Set of Diffusers
-Neutral and second order Filters
-2 Deuterium Lamps
-4 Tunsgten Ribbon Lamps
-1 Hollow Cathode Lamp, filled with argon.
Calibration Lamps with their associated Optical Fibres
Deuterium lamps are used for intensity calibration of the UV channel.
Tungsten lamps are used for intensity calibration of the visible and IR channels.
The Hollow Cathode lamp is used for wavelength calibration of the UV and visible channels and to know the instrument bandwidth.
The thermal items are:
- a Multi Layers Insulation
-a Radiator (top face)
-Internal Heaters with Thermostats
Seven stepper motors drive the internal mechanisms:
• the Main Shutter
• UV and Vis/IR Shutters
• UV, visible and IR Filters Wheels
• Gratings Rotating System
SOLSPEC General Drawing
Diffusers are placed in front of the entrance slit to ensure full illumination of the first grating and also to reduce the effect of pointing uncertainties during the observations.
II- Description
The instrument contains 7 lamps for checking the responsivity and the spectral characteristics of the spectrometers, thus allowing periodical verification to be made on the ground and in orbit.
MAIN CHARACTERISTICS
-Dimension: 436 mm x 437 mm x 455 mm
-Weight: 29 kg
-Power: 50 W nominal
80 W max.
-Field of Vue: ± 3°
- Interface: RS422
ELECTRONICS - Block Diagram
III- Ground Support Equipment
SOLSPEC is connected to a PC Sony Vaio (Windows XP) via a serial link RS-232.
The data (scientific and housekeeping) are displayed and stored automaticlly on its hard disk.
SOLSPEC Optical Schematics