Ellen Riddle Taylor

Evaluation of multidisciplinary design optimization techniques as applied to spacecraft design

The application of optimization to spacecraft design has the potential to significantly improve decision-making capabilities early in the design process. Successful integration of optimization and system-level spacecraft tools allow the concept architecture, technology choices, and performance requirements to be adjusted to meet an overall estimated cost goal; thereby enabling spacecraft design to be completed in a reliable, economical and timely manner.

ICON: Where earth's weather meets space weather

The Ionospheric Connection Explorer (ICON) is a NASA Heliophysics Explorer Mission designed to study the ionosphere, the boundary between Earth and space. This region, where ionized plasma and neutral gas collide and react, exhibits dramatic variability that affects space-based technological systems like GPS. The ionosphere has long been known to respond to space weather drivers from the sun, but recent NASA missions have shown this variability often occurs in concert with weather on our planet. This paper addresses the overall mission design and architecture of ICON, system design trades that have occurred through phase B of development, and challenges unique to the ICON mission. Set to launch in June 2017, ICON will perform a two-year mission to observe conditions in both the thermosphere and ionosphere. ICONs science objectives are to: 1) understand the source of strong ionospheric variability, 2) the transfer of energy and momentum from our atmosphere into space, and 3) how solar wind and magnetospheric effects modify the internally-driven atmosphere-space system. ICON will accomplish these 3 science objectives using a suite of 4 instruments mounted to a composite deck aboard an Orbital Sciences Corporation LEOstar-2 spacecraft bus. Dual Michelson Interferometers for Global High Resolution Thermospheric Imaging (MIGHTI) will measure neutral winds in the thermosphere, and temperatures at the boundary of space. Two Ion Velocity Meters (IVM) will measure in situ ion drifts in the ionosphere. Two ultraviolet spectrographic imagers, a Far Ultraviolet (FUV) and an Extreme Ultraviolet (EUV), will observe the airglow layers in the upper atmosphere in order to determine both the ionospheric and thermospheric density and composition. Finally, the current state of the program will be summarized and the projects plans for the future will be discussed.

EUV detector of the Cosmic Hot Interstellar Plasma Spectrometer

We describe the design and development of the CHIPS microchannel plate detector. The Cosmic Hot Interstellar Plasma Spectrometer will study the diffuse radiation of the interstellar medium in the extreme ultraviolet band pass of 90Å to 260Å. Astronomical fluxes are expected to be low, so high efficiency in the band pass, good out-of-band rejection, low intrinsic background, and minimal image non-linearities are crucial detector properties. The detector utilizes three 75mm diameter microchannel plates (MCPs) in an abutted Z stack configuration. A NaBr photocathode material deposited on the MCP top surface enhances the quantum detection efficiency. The charge pulses from the MCPs are centroided in two dimensions by a crossed-delayline (XDL) anode. A four panel thin-film filter array is affixed above the MCPs to reduce sensitivity to airglow and scattered radiation, composed of aluminum, polyimide/boron, and zirconium filter panes. The detector is housed in a flight vacuum chamber to preserve the hygroscopic photocathode, the pressure sensitive thin-film filters, and to permit application of high voltage during ground test.

Performance of the Cosmic Hot Interstellar Plasma Spectrometer

The Cosmic Hot interstellar Plasma Spectrometer (CHIPS), successfully launched on 2003 January 12, provides astronomers with an observatory dedicated to observation of the hot interstellar medium in the extreme ultraviolet. We describe here the otpical and photometric performance of the spectrograph based on calibrations of the individual components, end-to-end vacuum tests, and in-orbit observations of the Moon.

Optics design and performance for the Cosmic Hot Interstellar Plasma Spectrometer(CHIPS)

The CHIPS observatory was launched on 12 January 2003, and is the first UNEX (NASA Goddard Spaceflight Center University Explorer class) mission. It is currently on-orbit and performing diffuse spectroscopy in the 90-260Å wavelength band. The instrument is integrated with a custom 3-axis stabilized mini-satellite, designed for roughly one year of operation. The purpose of the observatory is examination of details of the local bubble thermal pressure, spatial distribution and ionization history. The spectrometer consists of six spectrograph channels which deliver >lambda/100 resolution spectra to a single detector. Cost constraints of UNEX led to a design based on a traditional aluminum structure, and an instrument with a large field of view (5° x 26°) for the dual purpose of increasing sensitivity in the photon-starved 90-260Å band, and to reduce requirements on spacecraft pointing. All optomechanical systems on the spectrometer, including coalignment, thermal, front cover and vacuum door release are performing well on orbit. We discuss design, test and operational performance of these systems, as well as launch loads and thermal system considerations.

CHIPS Microsatellite Optical System : Lessons Learned

The Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) observatory launched on 12 January 2003, and was the first and only successful GSFC UNEX (NASA Goddard Spaceflight Center University Explorer class) mission. The UNEX program was conceived by the National Aeronautics and Space Administration (NASA) as a new class of Explorer mission charged with demonstrating that significant science and/or technology experiments can be performed by small satellites with constrained budgets and a limited schedule. The purpose of the observatory was to examine details of the local bubble thermal pressure, spatial distribution and ionization history. The observatory was also used to observe solar spectra, both scattered from the Lunar surface and via a fortuitous 2nd order scattering path. CHIPS confirmed that spectral features within the 90-260Å band were much dimmer than was predicted by contemporary theories, and operated four years beyond its design lifetime. The observatory was placed in an extended safe-hold mode in April of 2008 for budgetary purposes. The spectrometer consisted of six spectrograph channels which delivered >λ/100 resolution spectra to a single detector. Cost constraints of UNEX led to a design based on a traditional aluminum structure, and an instrument with a large field of view (5° x 26°). All optical and optomechanical systems on the spectrometer performed flawlessly on orbit. We discuss the challenges, difficulties and lessons learned during the design, fabrication and execution stages of the mission.