The Avalanche Photodiode X-ray Spectrometer (AXS) is an optics free spectrometer operating in the 400 eV - 10 keV energy range. The purpose of the instrument is to measure the solar full disk irradiance from .1 to 2 nm with a spectral resolution on the order of ΔE/E equal to approximately 15%. This spectral region is a key and highly variable energy source to the lower thermosphere. The instrument was developed for sounding rocket use and, in addition to the science objectives, is used for underflight calibration of National Oceanic and Atmospheric Administration (NOAA) Geostationary Operational Environmental Satellite (GOES) X-ray instruments. Photon events from an avalanche photodiode produce electron showers that are detected by analog electronics. Pulse height analysis yields the energy of the impacting photon. By recording the number of events per pulse height bin, the AXS produces a spectrum. This instrument has been developed at the University of Alaska (UAF) and was flown on a sounding rocket on October 15, 2004. Calibrations were performed at the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF) III facility in Gaithersburg Maryland. In this paper the instrument design and calibration are discussed as well as both laboratory and rocket flight measurements.
In this paper, a 1.5 micron, 3-D scanning, portable and eyesafe aerosol lidar system is presented. The design, testing and field measurements of this lidar are introduced. An aerosol lidar model is used to evaluate lidar system's performance. At the end, the experimental and theoretic atmospheric detection results are presented and compared.
The Solar EUV Experiment (SEE) on the NASA Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics (TIMED) mission will measure the solar vacuum ultraviolet (VUV) spectral irradiance from 0.1 to 200 nm. To cover this wide spectral range two different types of instruments are used: a grating spectrograph for spectra between 25 and 200 nm with a spectral resolution of 0.4 nm and a set of silicon soft x-ray (XUV) photodiodes with thin film filters as broadband photometers between 0.1 and 35 nm with individual bandpasses of about 5 nm. The grating spectrograph is called the EUV Grating Spectrograph (EGS), and it consists of a normal- incidence, concave diffraction grating used in a Rowland spectrograph configuration with a 64 X 1024 array CODACON detector. The primary calibrations for the EGS are done using the National Institute for Standards and Technology (NIST) Synchrotron Ultraviolet Radiation Facility (SURF-III) in Gaithersburg, Maryland. In addition, detector sensitivity and image quality, the grating scattered light, the grating higher order contributions, and the sun sensor field of view are characterized in the LASP calibration laboratory. The XUV photodiodes are called the XUV Photometer System (XPS), and the XPS includes 12 photodiodes with thin film filters deposited directly on the silicon photodiodes' top surface. The sensitivities of the XUV photodiodes are calibrated at both the NIST SURF-III and the Physikalisch-Technische Bundesanstalt (PTB) electron storage ring called BESSY. The other XPS calibrations, namely the electronics linearity and field of view maps, are performed in the LASP calibration laboratory. The XPS and solar sensor pre-flight calibration results are primarily discussed as the EGS calibrations at SURF-III have not yet been performed.
The solar EUV experiment (SEE) selected for the NASA Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics mission will measure the solar vacuum UV (VUV) spectral irradiance from 0.1 to 200 nm. To cover this wide spectral range two different types of instruments are used: grating spectrograph for spectra above 25 nm and a set of silicon soft x-ray (XUV) photodiodes with thin film filters for below 30 nm. Redundant channels of the spectrograph and XUV photodiodes provide in-flight calibration checks on the time scale of a week, and annual rocket underflight measurements provide absolute calibration checks traceable to radiometric standards. Both types of instrument have been developed and flight proven as part of a NASA solar EUV irradiance rocket experiment.
The student nitric oxide explorer (SNOE) is a small satellite to be designed built and operated at the University of Colorado under the student explorer demonstration initiative from the University's Space Research Association (STEDI). The goal of the STEDI program is to demonstrate that low cost satellite missions can be done with large student involvement. The primary science goals of SNOE are to measure thermospheric nitric oxide (NO) and its variability over the lifetime of the mission. SNOE will also monitor the solar irradiance at soft x-ray wavelengths and the auroral energy deposition at high latitudes. Three science instruments are required to achieve the simultaneous measurements: an ultraviolet spectrometer for NO; a solar soft x-ray photometer; and a far ultraviolet photometer for studying the aurora. The instruments are designed to represent a minimum impact on the spacecraft, particularly in terms of data storage and interactions with the command and data handling system. The focus of this paper is the outline of the design of the science instruments. We discuss why these instruments are well suited for smaller, lower cost satellite missions.
The Student Nitric Oxide Explorer (SNOE) is a small scientific spacecraft designed to launch on a Pegasus<SUP>TM</SUP> XL vehicle for the Student Explorer Demonstration Initiative. Its scientific goals are to measure nitric oxide density in the lower thermosphere and to analyze the solar and magnetospheric influences that create it and cause its abundance to vary dramatically. The SNOE ('snowy') spacecraft and instrumentation is being designed and built at the University of Colorado Laboratory for Atmospheric and Space Physics (LASP) by a team of scientists, engineers, and students. The spacecraft is a compact hexagonal structure, 37' by 39', weighing approximately 280 lbs. It will be launched into a circular orbit, 550 km altitude, 97.5 degrees inclination for sun-synchronous precession at 10:30 AM ascending node. It is designed to spin at 5 rpm with the spin axis normal to the orbit plane. It carries three instruments: an ultraviolet spectrometer to measure nitric oxide altitude profiles on the limb, a two-channel ultraviolet photometer to measure auroral emissions in the nadir, and a five-channel solar soft x-ray photometer. An experimental GPS receiver is also included. The spacecraft structure is aluminum, with a center platform section for the instruments and subsystems. Static solar arrays are supported by a truss system. A spacecraft microprocessor handles all subsystem, instrument, and communications functions in an integrated fashion, including command decoding, attitude control, instrument commanding, data storage, and telemetry. The spacecraft is scheduled for launch in early 1997 and will be operated by students at LASP. For more information on the SNOE project, please visit http://lasp.colorado.edu/snoe/.
A NASA sounding rocket experiment was developed to study the solar extreme-ultraviolet (EUV) spectral irradiance and its effect on the upper atmosphere. Both the solar flux and the terrestrial molecular nitrogen via the Lyman-Birge-Hopfield bands in the far-ultraviolet (FUV) region were measured remotely from a sounding rocket on October 27, 1992. The rocket experiment also includes EUV instruments from Boston University, but only the National Center for Atmospheric Research's (NCAR)/University of Colorado's (CU) four solar instruments and one airglow instrument are discussed. The primary solar EUV instrument is a 0.25-m Rowland circle EUV spectrograph that has flown on three rockets since 1988 measuring the solar spectral irradiance from 30 to 110 nm with 0.2-nm resolution. Another solar irradiance instrument is an array of six silicon soft x-ray (XUV) photodiodes, each having different metallic filters coated directly on the photodiodes. This photodiode system provides a spectral coverage from 0.1 to 80 nm with ~15-nm resolution. The other solar irradiance instrument is a silicon avalanche photodiode coupled with pulse height analyzer electronics. This avalanche photodiode package measures the XUV photon energy, providing a solar spectrum from 50 to 12,400 eV (25 to 0.1 nm) with an energy resolution of about 50 eV. The fourth solar instrument is an XUV imager that images the sun at 17.5 nm with a spatial resolution of 20 arc sec. The airglow spectrograph measures the terrestrial FUV airglow emissions along the horizon from 125 to 160 nm with 0.2-nm spectral resolution. The photon-counting CODACON detectors are used for three of these instruments and consist of coded arrays of anodes behind microchannel plates.
A sounding-rocket experiment is being developed for the study of EUV spectral irradiance and its effects on the upper atmosphere, using three solar EUV instruments devised by the Laboratory for Atmospheric and Space Physics. These include a 25-cm Rowland circle EUV spectrograph, an array of Si X-UV photodiodes, and an X-UV imager with 20 arcsec resolution of the sun.