High resolution calibrated near infrared (NIR) imagery of the Space Shuttle Orbiter was obtained during hypervelocity
atmospheric re-entry of the STS-119, STS-125, STS-128, STS-131, STS-132, STS-133, and STS-134 missions. This
data has provided information on the distribution of surface temperature and the state of the airflow over the windward
surface of the Orbiter during descent. The thermal imagery complemented data collected with onboard surface
thermocouple instrumentation. The spatially resolved global thermal measurements made during the Orbiter's
hypersonic re-entry will provide critical flight data for reducing the uncertainty associated with present day ground-to-flight
extrapolation techniques and current state-of-the-art empirical boundary-layer transition or turbulent heating
prediction methods. Laminar and turbulent flight data is critical for the validation of physics-based, semi-empirical
boundary-layer transition prediction methods as well as stimulating the validation of laminar numerical chemistry
models and the development of turbulence models supporting NASA's next-generation spacecraft. In this paper we
provide details of the NIR imaging system used on both air and land-based imaging assets. The paper will discuss
calibrations performed on the NIR imaging systems that permitted conversion of captured radiant intensity (counts) to
temperature values. Image processing techniques are presented to analyze the NIR data for vignetting distortion, best
resolution, and image sharpness.
The Bi-static Optical Imaging Sensor (BOIS) is a 2-D imaging sensor that operates in the short-wave infra-red (SWIR)
spectral regime over wavelengths from approximately 1.0 to 2.4 microns. The conceptual design of the sensor is based
on integral field spectroscopy techniques. The BOIS sensor utilizes a fiber transition element consisting of multiple
optical fibers to map the 2-D spatial input scene into a 1-D linear array for injection into a hyper-spectral imaging (HSI)
sensor. The HSI spectrometer acquires fast time resolution snapshots (60 Hz) of the entire input target scene in
numerous narrowband spectral channels covering the SWIR spectral band. The BOIS sensor is developed to spatially
observe the fast time-evolving radiative signature of targets over a variety of spectral bands, thus simultaneously
characterizing the overall scene in four dimensions: 2 spatial, wavelength, and time.
We describe the successful design, operation, and testing of a laboratory prototype version of the BOIS sensor as well as
further development of a field version of the sensor. The goal of the laboratory prototype BOIS sensor was to validate
the proof-of-concept ability in the 4-D measurement concept of this unique design. We demonstrate the 2-D spatial
remapping of the input scene (using SWIR laser and blackbody cavity sources) in multiple spectral channels from the
spatial versus spectral pixel output of the HSI snapshot. We also describe algorithms developed in the data processing to
retrieve temperatures of the observation scene from the hyper-spectral measurements.
As part of the Triana mission, the Scripps Earth Polychromatic Imaging Camera (Scripps-EPIC) will view the full sunlit side of Earth from the Lagrange-1 point. The National Institute of Standards and Technology and the Scripps Institution of Oceanography, in collaboration with the contractor, Lockheed-Martin, planned the radiometric calibration of Scripps-EPIC. The measurements for this radiometric calibration were selected based upon the optical characteristics of Scripps-EPIC, the measurement equation relating signal to spectral radiance, and the available optical sources and calibrated radiometers. The guiding principle for the calibration was to perform separate, controlled measurements for each parameter in the measurement equation, namely dark signal, linearity, exposure time, and spectral radiance responsivity.
We describe an instrument package to remotely measure thermospheric, exospheric, and plasmaspheric structure and composition. This instrument was flown aboard the second test flight of the Black Brant XII sounding rocket on December 5, 1989, which attained an apogee of 1460 km. The experiment package designed for this flight consisted of a spectrophotometer to measure He I 584-Å, O II 834-Å, a I 989-Å, hydrogen Lyman β (1025-Å), hydrogen Lyman α (1216-Å), and O I 1304-Å emissions, and a photometer to measure the He II 304-Å emission. The optical design of the spectrophotometer was identical to that of the Berkeley Extreme Ultraviolet (EUV) Airglow Rocket Spectrometer payload, flown on September 30, 1988, aboard the maiden flight of the Black Brant XII rocket. The He II 304-Å photometer consisted of a layered synthetic microstructure mirror tuned at 304 Å in a Wadsworth-type mount acting as a light bucket to focus incident radiation through a thin-film metal filter onto a channeltron detector. We also present the initial data analysis and describe directions we will go toward the completion of our study.
We constructed a high-resolution imaging spectrograph for use as a payload in a sounding rocket experiment. The spectrograph employs a modified Ebert-Fastie design with a LiF objective prism and a replica of an El echelle grating developed for the Space Telescope Imaging Spectrograph. The instrument has a 5-arcmin-long adjustable width entrance aperture with two identical secondary apertures separated from the primary by ±2 arcmin. The secondary apertures are intended for simultaneous measurement of the sky background. The spectrograph has been optimized for measurement of the 221st order of Lyman-α at a resolution of 0.03 to 0.04 Å. The detector system is a two-dimensional photon counting device that employs a microchannel plate intensifier and a wedge and strip anode readout. The spectrograph is used as a focal plane instrument of the Jupiter Telescope, a Cassegrain telescope constructed exclusively for use as a sounding rocket payload. The Jupiter Telescope is self-pointed, employing image motion compensation to achieve 2- to 3-arc sec image quality. The telescope/spectrograph payload was launched from the White Sands Missile Range on May 4, 1991, to observe the H Lyman-α line profile spatially resolved across the disk of Jupiter in the North-South (polar) and East-West (equatorial) directions, and to measure the H Lyman-α emission line profile from interplanetary hydrogen associated with the local insterstellar medium.
We describe an instrument package to remotely measure thermospheric, exospheric, and plasmaspheric structure and composition. This instrument was flown aboard the second test flight of the Black Brant XII sounding rocket on December 5, 1989, which attained an apogee of 1460 km. The experiment package consisted of a spectrophotometer to measure He I 584 A, O II 834 A, O I 989 A, hydrogen Lyman beta (1025 A), hydrogen Lyman alpha (1216 A), and O I 1304 A transitions, and a photometer to measure the He II 304 A emission. The optical design of the spectrophotometer was identical to that of the Berkeley Extreme Ultraviolet (EUV) Airglow Rocket Spectrometer payload, flown on September 30, 1988 aboard the maiden flight of the Black Brant XII rocket. We present the initial data analysis and describe directions we will go toward the completion of our study.
We have constructed a high resolution imaging spectrograph for use as a payload in a sounding rocket experiment. The spectrograph employs a modified Ebert-Fastie design using a LiF predispersing prism and a replica of the E1 echelle grating developed for the Space Telescope Imaging Spectrograph. The spectrograph is used as a focal plane instrument of the Jupiter Telescope, a Cassegrain telescope constructed exclusively for use as a sounding rocket payload. The telescope and spectrograph were launched from the White Sands Missile Range on May 4, 1991 to observe the H Ly-alpha line profile spatially resolved across the disk of Jupiter in the north-south and east-west directions, and to measure the H Ly-alpha emission line profile from interplanetary hydrogen associated with the local interstellar medium.
Spaceflight optical instruments have two conflicting requirements. They need to be both rigid and lightweight. In addition, for interferometric far ultraviolet spectrometers, the requirements for precision positioning are more severe than for conventional spectrometers. To meet the challenge of lightweight optical instruments, a modular adjustment mechanism was developed to position two orthogonal axes of a universal three-axis gimbal support system with a positioning accuracy on the order of 10 arc seconds. The mechanism was designed as a self-contained assembly which can be removed after final alignment of a spacebound optical instrument to reduce its in-flight mass. To demonstrate the concept, a number of these assemblies were made and mounted on two of the positioning axes of a far ultraviolet spatial heterodyne interferometer. A shaft clamp was used on each positioning axis to retain the adjusted position. This paper describes the design of the mechanism and presents optical test results.
Requirements for spaceflight optical instruments usually dictate that for the structures be rigid, lightweight, and thermally stable. In addition, for interferometric far ultraviolet (FUV) spectrometers, the requirements for torsional deflection are more severe than with conventional spectrometers. To meet the challenge for rigid and lightweight optical instruments, this paper explores the design of a high-stiffness structure for the support of an FUV spatial heterodyne interferometer where the torsional deflection of the instrument is on the order of 10 arc seconds. The structure is based on use of a thin, hollow section beam with weight-relieving between optical elements. The design also uses a modular and self-contained positioning mechanism that is removed after final optical alignment. Several specific material properties are presented as criteria for material selection. The parameters which affect the particular design requirements are identified with respect to the desired material properties and physical design features. Although large thin sections are susceptible to thermal gradients, this could be minimized by a trade-off for weight, where adequate margin exists. This paper describes the preliminary design for the structure and presents an analysis to verify compliance with the requirements.
An all-reflection spatial heterodyne spectrometer (SHS) has been recently developed. The advantages over conventional high-resolution grating spectrometers are that the SHS requires no mechanical scanning, a self-compensating optical design permits easy alignment, and it is much smaller than other spectrometers of comparable resolution. Since all beam-splits and recombinations occur by reflection off of a diffraction grating, the interferometer is capable of operating well into the extreme ultraviolet (EUV) and possibly into the soft X-ray region. A description of the design and the characteristics of the instrument is presented. Also, test results, including sample interferograms as well as their Fourier-transformed spectra, at both visible and UV wavelengths are shown. Finally, we report on future developments and possible applications.
A need has arisen for efficient, blazed, symmetric gratings for use as beam splitters in far and extreme ultraviolet interferometers. In particular, the development of an all-reflection, far ultraviolet spatial heterodyne interferometer can benefit tremendously from such a grating. To fulfill this need, we have manufactured a mechanically ruled grating with a V-groove profile blazed for H Lyman-alpha at 1216 A. We present the grating performance at Lyman-alpha in the context of its application to the spatial heterodyne interferometer.
We discuss a high resolution microchannel plate (MCP) imaging detector to be used in measurements of Doppler-shifted hydrogen Lyman-alpha line emission from Jupiter and the interplanetary medium. The detector is housed in a vacuum-tight stainless steel cylinder (to provide shielding from magnetic fields) with a MgF2 window. Operating at nominal voltage, the four plate configuration provides a gain of 1.2 x 10 exp 7 electrons per incident photon. The wedge-and-strip anode has two-dimensional imaging capabilities, with a resolution of 40 microns FWHM over a one centimeter diameter area. The detector has a high quantum efficiency while retaining a low background rate. A KBr photocathode is used to enhance the quantum efficiency of the bare MCPs to a value of 35 percent at Lyman-alpha.