Instrument Overview

Instrument Overview

SEE Instrument with Labels
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SEE is an experiment designed to measure the full-disk solar irradiance from 0.1 to 200 nm using a grating pectrograph and silicon photodiodes coated with thin film transmission filters. The spectral resolution of the measurements is 0.4 nm above 25 nm and about 7 nm below 25 nm. The solar sensors are designed to let the Sun drift through their field of view once per orbit, so only an one-axis pointing platform is employed for SEE.

SEE is being designed and built primarily at the LASP Space Technology Building. The only major subcontract for the SEE instruments is to Schaeffer Magnetics, Inc. for the SEE pointing platform hardware.

TIMED SEE Instrument Components

EUV Grating Spectrograph (EGS)
The EGS is a Rowland-circle grating spectrograph that makes solar extreme ultraviolet (EUV) spectral irradiance measurements. The original EGS made measurements from 30 to 115 nm with 0.2 nm spectral resolution. This EGS version made measurements on sounding rockets in 1988, 1989, 1992, 1993, and 1994, and then it was lost during the failure of the Conestoga / METEOR satellite launch in 1995. The new EGS, the TIMED SEE protoflight version, covers the spectral range from 25 to 200 nm with 0.4 nm spectral resolution. This protoflight EGS made a solar irradiance measurement in May 1997 on a sounding rocket.

XUV Photometer System (XPS)
A set of 12 silicon photodiodes with metallic thin films deposited directly on the diodes is used to measure the solar soft X-ray (XUV) irradiance. The XPS spectral range is from 0.1 to 35 nm with each photometer having a spectral bandpass of 5 to 10 nm. The original XPS has flown on sounding rockets in 1992, 1993, and 1994, and they were lost also on the failed METEOR satellite launch. The new XPS was rebuilt as the TIMED SEE protoflight version with same spectral range as the original XPS. This protoflight XPS made a solar irradiance measurement in May 1997 on a sounding rocket. To view the expected sensitivity of the various XPS diodes, click on the following link: XPS Coating Plots

SEE Solar Pointing Platform (SSPP)
The SSPP is a one-axis pointing platform that incorporates a harmonic drive from Schaeffer Magnetics, Inc. The SEE instruments are designed to let the Sun drift through their field of view by the spacecraft motion. The SSPP controls the angle for that drift with 1 arc-min precision.

Microprocessor Unit (MU)
The MU consists of a 1750 processor, memory, and instrument data and power interfaces. The MU is being developed at LASP using much of the design from the Cassini UVS microprocessor design.

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