A new Fabry-Perot interferometer was built and later deployed at Resolute, Canada (75° N), the future site of the National Science Foundation Advanced Modular Incoherent Scatter Radar (AMISR). The new instrument is designed to measure mesospheric and lower thermospheric tidal waves and the upper thermosphere polar cap convection pattern using OH, O 5577 Å and 6300 Å emissions. The wind errors for these emissions are 6 m/s (3 minute integration), 1 m/s (3 minute) and 2-6 m/s (5 minute), respectively. The instrument was tested in Boulder, Colorado and measurement results are compared with nearby LIDAR mesospheric neutral wind measurements. The comparison showed good agreement between the two instruments. Neutral wind data obtained at Resolute also demonstrate that the instrument meets the design goal and is able to provide high quality data for future studies of mesospheric and lower thermospheric dynamics as well as magnetospheric-ionospheric coupling, along with ion-neutral coupling in the upper atmosphere of the polar cap. This report describes the basic design and initial results from this instrument.
Wilbert Skinner, Rick Niciejewski, Timothy Killeen, Stanley Solomon, Daniel Gablehouse, Qian Wu, David Ortland, David Gell, Alan Marshall, Edwin Wolfe, Marie Cooper, Julie Kafkalidis
The TIMED Doppler Interferometer (TIDI) is a Fabry-Perot interferometer designed to measure winds in the mesosphere and thermosphere (60-180 km) as part of the TIMED mission. TIDI is a limb viewer and observes emissions from OI 557.7 nm and rotational lines in the O2(0-0) Atmospheric band. Wind measurement accuracies approach 3 ms-1 in the mesosphere and 15 ms-1 in the thermosphere. The TIDI instrument’s performance during the first year and a half of operation is discussed in this paper. Many subsystems are working as designed. The thermal control system is holding the instrument temperatures at
their desired set-points. The CCD detector is working as expected with no changes observed in the gain, bias or read noise. The instrument suffers from a light leak that causes the background to be elevated and increases the uncertainty in the wind measurement. Nothing can be done to eliminate this problem but modeling of the background has eliminated any systematic effect. Water outgassing from the spacecraft or instrument has deposited as ice on some part of the optics and reduced the instrument’s sensitivity. This
problem has been reduced by two spacecraft rolls which pointed the TIDI radiator to view more of the earth causing the optics to warm up and sublimate much of the ice.
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.
Stanley Solomon, Charles Barth, Penina Axelrad, Scott Bailey, Ronald Brown, Randal Davis, Timothy Holden, Richard Kohnert, Frederick Lacy, Michael McGrath, Darren O'Connor, Jeffrey Perich, Heather Reed, Mark Salada, John Simpson, Jeffrey Srinivasan, George Stafford, Stephen Steg, Gail Tate, James Westfall, Neil White, Peter Withnell, Thomas Woods
The Student Nitric Oxide Explorer (SNOE) is a small scientific spacecraft designed to launch on a PegasusTM 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/.
David Rusch, Charles Barth, R. Todd Clancy, Stanley Solomon, George Lawrence, William McClintock, Cora Randall, Gary Thomas, Rolando Garcia, Raymond Roble, Jean-Claude Gerard
The temperature-ozone-nitric oxide experiment (TONE) on the thermosphere, ionosphere, mesosphere, energetics, and dynamics (TIMED) mission consists of two ultraviolet spectrometers and an infrared photometer. A medium resolution spectrometer (MRS) covers the spectral region from 210 to 247 nm with 0.2 nm resolution, and a low resolution spectrometer/infrared photometer (LRS/IRP) covers the 235 to 320 nm region with 2.0 nm resolution, and measures the 1.27 micron emission from molecular oxygen excited by ozone photolysis. The Earth's limb is scanned by articulation mirrors which also serve as the field- of-view limiting elements. The TONE measures profiles of emission as a function of altitude on the Earth's limb. The primary measurements include profiles of Rayleigh scattered sunlight and 1.27 micron emission in the mesosphere and lower thermosphere, and fluorescent emission from nitric oxide in the upper mesosphere and thermosphere. The inverted radiance measurements will yield profiles of temperature, density, and ozone in the mesosphere, and temperature and nitric oxide density in the thermosphere with 2.5 km vertical resolution and 4.5 degree spatial resolution along the orbital path. The primary TONE measurements extend from 50 to 180 km and are fundamental to the science objectives of the TIMED mission. The broad capabilities of the TONE contribute significantly to the TIMED mission with a low-cost, highly reliable instrument based on a long heritage of space instruments built at the University of Colorado's Laboratory for Atmospheric and Space Physics. The TONE has heritage from spectrometers on Mariner 9, Pioneer Venus, the Solar Mesosphere Explorer, Galileo, and Cassini.
The Solar EUV Experiment (SEE) selected for 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 above 25 nm and an avalanche photodiode for spectra below 25 nm. As part of the in-flight calibration plan, silicon XUV photodiodes with thin film filters are used as stable broadband photometers between 0.1 and 40 nm. In addition, redundant spectrograph and avalanche photodiode capabilities provide calibration checks on the time scale of a month, and annual rocket underflight measurements provide absolute calibration checks traceable to NIST photometric standards. All three types of instruments have been developed and flight proven as part of a NASA solar EUV irradiance rocket experiment.
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.
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