Mathematics – Logic
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sa41a08p&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #SA41A-08 INVITED
Mathematics
Logic
0310 Airglow And Aurora, 0355 Thermosphere--Composition And Chemistry, 0358 Thermosphere--Energy Deposition, 0394 Instruments And Techniques, 2704 Auroral Phenomena (2407)
Scientific paper
Any observational investigation of a physical phenomenon is confronted with a choice of the temporal and spatial scales to be observed. For observations from a space platform these choices are further constrained by total cost, with its collateral restrictions on payload and instrument size, mass, power, data rate, and choice of orbit. When one posits an investigation of the polar upper atmosphere the choice of orbit is often the determining factor in the design of the instruments. Optical instruments designed for auroral imaging are driven by the desire to image as much of the auroral oval as possible. Choices about bandpasses (the nominal range of sensitivity) have to be made and one commonly encounters far ultraviolet (FUV) instruments. The FUV is chosen because there is no signal from the atmosphere below about 80 km, thus enabling one to make observations of the sunlit aurora. The principle limitations of FUV optical design are the low transmission efficiency of suitable optical materials (glasses and plastics have 0% transmission in the FUV, for example, while commonly used materials have transmissions below 30% for useful thicknesses) and the relatively low reflection efficiency of optical surfaces (this provides a strong impetus towards reducing the total number of reflections since the efficiency if the product of all the reflection efficiencies). From high Earth orbit a camera, that is to say a broadband imager, seems a natural choice as, in principle, such a device can provide continuous imaging at good spatial resolution of the entire oval with reasonable sensitivity. Camera designs have three principle problems: 1) providing a uniform response over the entire image, 2) meeting out of band rejection requirements (i.e. not being sensitive to other than FUV light), and 3) providing images at more than one wavelength simultaneously. These last two problems stem from the use of the combination of filters, mirror coatings, and photocathodes to define the instrument's band pass. From low Earth orbit, such as that of the US Air Force Defense Meteorological Satellite Program (DMSP) satellites that operate at 830 km altitude, or the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission at 625 km, other approaches have to be adopted to maximize the amount of the aurora that can be imaged. The Special Sensor Ultraviolet Spectrographic Imager (SSUSI) on DMSP and the Global Ultraviolet Imager (GUVI) on TIMED are examples of an approach that seeks to maximize auroral coverage, responsivity, spectral "purity", and number of simultaneous wavelengths covered. Each general class of sensor has its advantages and issues. In combination, HEO and LEO sensors provide powerful tools for probing the Earth's atmosphere, particularly the polar upper atmosphere and auroral phenomena. In this talk I will summarize the status of the SSUSI and GUVI projects, their data products, how and when these validated data products will be made available, and plans for coordinated observations with ground sites and other space assets. These new sensors, that should fly begining this summer and will provide continuous auroral imagery from LEO for the next ten years, meet their own objectives as well as providing key measurements for the Sun-Earth Connections and Living With a Star Programs.
No associations
LandOfFree
Observing the Polar Upper Atmosphere from Low Earth Orbit: Challenges, Opportunities, and New Missions does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Observing the Polar Upper Atmosphere from Low Earth Orbit: Challenges, Opportunities, and New Missions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Observing the Polar Upper Atmosphere from Low Earth Orbit: Challenges, Opportunities, and New Missions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1272960