Earth’s ionosphere responds dynamically over a wide range of temporal and spatial scales to changes in the magnetosphere and solar wind from above, and to neutral atmospheric dynamics from below. Determining the dynamics and coupling of Earth's magnetosphere, ionosphere, and atmosphere by vector magnetic field measurements at all altitudes is essential, as the field plays a major role in controlling the distribution of ionospheric plasma. It is difficult to measure the magnetic B-field, either locally or globally, at the altitudes of the upper mesosphere and lower thermosphere (UMLT) where the transfer of energy and momentum between the plasma and neutral components of the system occur. The 118-GHz imaging magnetometer will measure all four Stokes parameters as a function of frequency about the Zeeman-split center of the 118-GHz molecular oxygen line. We are developing an array of fully-polarimetric millimeterwave radiometer/spectrometers operating near 118 GHz. These low cost, low power, low mass polarimetric 118 GHz millimeter-wave array receivers do not require cooling to meet the sensitivity requirements. With digital spectrometers we will be able to integrate the complete end-to-end system. This work will enable a second generation small satellite mission with an off-nadir viewing instrument comprised of 120 such receivers (arranged so that each spot on the Earth is observed simultaneously by four receivers each) that will globally map the magnetic field in the mesosphere at 42-76 km altitude at a horizontal resolution ~100 km with 1-sigma error of 40-120 nT, in typical mesospheric temperature conditions.
The Johns Hopkins University Applied Physics Laboratory (JHU/APL) is developing a compact, light-weight, and lowpower midwave-infrared (MWIR) imager called the Compact Midwave Imaging Sensor (CMIS), under the support of the NASA Earth Science Technology Office Instrument Incubator Program. The goal of this CMIS instrument development and demonstration project is to increase the technical readiness of CMIS, a multi-spectral sensor capable of retrieving 3D winds and cloud heights 24/7, for a space mission. The CMIS instrument employs an advanced MWIR detector that requires less cooling than traditional technologies and thus permits a compact, low-power design, which enables accommodation on small spacecraft such as CubeSats. CMIS provides the critical midwave component of a multi-spectral sensor suite that includes a high-resolution Day-Night Band and a longwave infrared (LWIR) imager to provide global cloud characterization and theater weather imagery. In this presentation, an overview of the CMIS project, including the high-level sensor design, the concept of operations, and measurement capability will be presented. System performance for a variety of different scenes generated by a cloud resolving model (CRM) will also be discussed.
The Johns Hopkins University Applied Physics Laboratory (JHU/APL) has created a unique design for a compact, lightweight, and low-power instrument called the Compact Midwave Imaging Sensor (CMIS). Funded by the NASA ESTO Instrument Incubator Program (IIP), the goal of this CMIS development project is to increase the technical readiness of CMIS for retrieval of cloud heights and atmospheric motion vectors using stereo-photometric methods. The low-cost, low size, weight and power (SWaP) CMIS solution will include high operating temperature (HOT) MWIR detectors and a very low power cooler to enable spaceflight in a 6U CubeSat. This paper will provide an overview of the CMIS project to include the high-level sensor design.
Obtaining temperature, pressure, and composition profiles along with wind velocities in the Earth’s
thermosphere/ionosphere system is a key NASA goal for understanding our planet. We report on the status of a
technology development effort to build an all-solid-state heterodyne receiver at 2.06 THz that will allow the
measurement of the 2.06 THz [OI] line for altitudes greater than 100 km. The receiver front end features low-parasitic
Schottky diode mixer chips that are driven by a local oscillator (LO) source using Schottky diode based multipliers. The
multiplier chain consists of a 38 GHz oscillator followed by a set of three cascaded triplers at 114 GHz, 343 GHz and
Long-term measurements of the global distributions of clouds, trace gases, and surface reflectance are needed for
the study and monitoring of global change and air quality. The Geostationary Imaging Fabry-Perot Spectrometer
(GIFS) instrument is an example of a next-generation satellite remote sensing concept. GIFS is designed
to be deployed on a geostationary satellite, where it can make continuous hemispheric imaging observations of
cloud properties (including cloud top pressure, optical depth, and fraction), trace gas concentrations, such as tropospheric
and boundary layer CO, and surface reflectance and pressure. These measurements can be made with
spatial resolution, accuracy, and revisit time suitable for monitoring applications. It uses an innovative tunable
imaging triple-etalon Fabry-Perot interferometer to obtain very high-resolution line-resolved spectral images of
backscattered solar radiation, which contains cloud and trace gas information. An airborne GIFS prototype and
the measurement technique have been successfully demonstrated in a recent field campaign onboard the NASA
P3B based at Wallops Island, Virginia. In this paper, we present the preliminary GIFS instrument design and
use GIFS prototype measurements to demonstrate the instrument functionality and measurement capabilities.
Long-term measurements of the global distribution of clouds and the surface reflectance are needed to provide inputs to climatological models for global change studies. The Geostationary Imaging Fabry-Perot Spectrometer (GIFS) instrument is a next-generation satellite concept, to be deployed on a geostationary satellite for continuous hemispheric imaging of cloud properties, including cloud top pressure, optical depth, fraction, and surface reflectance. This is an ideal approach to make these cloud property measurements with desired spatial resolution, accuracy, and revisit time. It uses an innovative tunable imaging triple-etalon Fabry-Perot interferometer to obtain images of high-resolution spectral line shapes of two O2 B-band lines in the backscattered solar radiation. The GIFS remote sensing technique takes advantage of the pressure broadening information embedded in the absorption line shapes to better determine cloud properties, especially for those clouds below 5 km. We present a preliminary instrument design, including the general instrument requirements.
Recent assessments of global climate change conclude that the radiative effect of aerosols is one of the largest uncertainties in our ability to predict future climate change. A myriad of new sensors and satellite missions are being designed to address this major question confronting credible prediction of climate change. The NASA Langley Airborne A-Band Spectrometer (LAABS) is a recently developed aircraft instrument that provides high spectral resolution (~0.03 nm) radiance measurements of reflected sunlight over the oxygen A-band spectral region centered near 765 nm. High resolution O2 A-band spectrometry of reflected sunlight is a promising new approach for remote sensing of aerosol and cloud optical properties. While the LAABS instrument provides valuable data on a stand-alone basis, greater scientific return may be realized by combining the A-band spectra with coincident lidar measurements that supply additional information on the vertical distribution of the aerosol. In particular, an instrument suite that combines LAABS with the new airborne High Spectral Resolution Lidar (HSRL) has the potential to provide a comprehensive suite of aerosol and cloud optical property measurements never before achieved. In this paper, we investigate the combined use of LAABS and HSRL measurements to infer aerosol single scatter albedo. We explore the information content of the O2 A-band reflectance spectra and, in particular, the advantages offered by high resolution A-band spectrometers such as LAABS. The approach for combined LAABS/HSRL retrievals is described and results from simulation studies are presented to illustrate their potential for retrieval of single scatter albedo.
The Thermosphere•Ionosphere•Mesosphere•Energetics and Dynamics (TIMED) program is developed by The Johns Hopkins University Applied Physics Laboratory (APL) for NASA as NASA's first Solar Terrestrial Probe mission in the Solar Connections program. It was successfully launched into its desired orbit on December, 7, 2001 and started its prime science mission in January 2002. TIMED employs four remote sensing instruments designed to provide measurements needed to characterize the temperature, density, and wind structures of the Earth's atmosphere extending from 60 to 180 kilometers and to understand the processes controlling the region's energy balance. TIMED is a low-cost mission and its spacecraft was designed with a high degree of autonomy to enable inexpensive Mission Operations using a relatively small Mission Operations Team. The keys to enabling this cost savings are the decoupled instrument operations approach based on real-time GPS navigation and event based
instrument commanding on board the spacecraft. This paper provides an overview of the TIMED mission, mission architecture, spacecraft and ground system design. The focus of this discussion will be on cost reduction efforts, especially those related to advanced technology and the enabling concept of decoupled mission operations.
The Stellar Absorption and Refraction Sensor (STARS) is a compact, large-aperture instrument that combines a UV-IR imaging spectrograph with a co-aligned visible-light imager to make simultaneous absorptive and refractive stellar occultation measurements. The absorption measurements provided by the spectrograph allow the determination of vertical profiles of atmospheric constituents. The coincident refraction observations made by the image yield high-precision measurements of atmospheric density, pressure, and temperature and provide independent knowledge of both the refracted light path and Rayleigh extinction, which are critical in reducing the uncertainty in the retrieved constituent profiles in the lower atmosphere. STARS employs a two-axis gimbaled telescope to acquire and track the star and a two-axis, high-precision, fast-steering mirror to correct for spacecraft jitter and maintain the star within the spectrograph field of view. The relative star position measured by the imager provides position feedback to the active tracking loop of the fast-steering mirror. With funding from NASA's Instrument Incubator Program, a laboratory facility has been developed to demonstrate the overall instrument performance and, in particular, its capability to acquire and track a setting, refracting, and scintillating star, to compensate for various degrees of platform jitter, and to provide the pointing knowledge required for accurate determination of the atmospheric quantities. The combination of built-in image tracking and motion compensation capabilities, small size, and limited spacecraft resource requirements makes STARS and its tracking mechanism suitable for deployment on existing and future commercial spacecraft platforms for applications that require high-precision pointing. In this paper, we present details of the instrument design and its expected performance based on our laboratory tests.
The Self-Calibrating H2O and O3 Nighttime Environmental Remote Sensor (SCHOONERS) is a compact, integrated UV-IR imaging spectrograph and imager. The instrument has a 25 cm diameter aperture and employs a two- axis gimbaled telescope to provide acquisition and tracking of the star. It also uses a two-axis high-precision vernier mirror to correct for spacecraft jitter and maintain the star within the field-of-view. The imaging spectrograph, covering a spectral range between 300 and 900 nm, measures the varying absorption of starlight as a star sets through the nighttime Earth's atmosphere to determine vertical profiles of atmospheric constituents. The relative star position measured by the co-aligned imager not only provides position feedback to the acting tracking loop of the vernier mirror, but also measures the star refraction angle for determining the atmospheric density and temperature profiles. The SCHOONERS scanning platform and its high- precision tracking mirrors provide 44 microradian azimuth pointing stability and 60 microrad altitude tracking accuracy (3(sigma) ). Its built-in image tracking and motion compensation mechanism, coupled with its small size and limited spacecraft resources required, makes it suitable for deployment on existing and future commercial spacecraft platforms as an instrument-of-opportunity after the year 2002. A laboratory facility has been developed to demonstrate the instrument performance, especially its capability to acquire and track a setting, refracting, and scintillating star, to compensate for various degrees of platform jitter, and to provide the pointing knowledge accuracy required for the determination of atmospheric density and temperature. Hardware includes an accurately moving variable intensity point source to simulate the star and motion stages to generate jitter at the instrument. Software simulates the stellar refraction, attenuation, and scintillation for a full end-to-end test of the instrument.
The Thermosphere (DOT) Ionosphere (DOT) Mesosphere (DOT) Energetics and Dynamics (TIMED) spacecraft being developed by The Johns Hopkins University Applied Physics Laboratory is the first mission in NASA's Solar Connections program. TIMED is a low-cost mission aimed at providing a basic understanding of the least explored and least understood region of the earth's environment, the atmospheric band extending from 60 to 180 kilometers in altitude. The TIMED suite of instruments is intended to determine the temperature, density, and wind structure in the Mesosphere, Lower Thermosphere and Ionosphere (MLTI) region including seasonal and latitudinal variations. TIMED is also intended to determine the relative importance of radiative, chemical, electrodynamic, and dynamic sources and sinks of energy for the thermal structure of the MLTI. This paper provides an overview of the TIMED mission, discussing science objectives, mission architecture, spacecraft and ground system design, and the decoupled mission operations concept. The focus of this discussion will be on cost reduction efforts, especially those related to advanced technology. This paper also provides a brief introduction to the four TIMED instruments (GUVI, SABER, SEE, and TIDI) and develops a context for understanding their common design elements.