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NASA NTRS1998

Acoustic Amplification in the Far Infrared Focal Plane Assembly of the Composite Infrared Spectrometer (CIRS) for the Cassini Mission to Saturn

The Composite Infrared Spectrometer (CIRS) of the Cassini mission to Saturn has two interferometers covering the far infrared FIR and mid infrared, MIR wavelength region. The FIR is a polarizing Michelson interferometer which presents a collimated output beam to the FIR focal plane. The focal plane consists of a parabolic focus mirror and an analyzer grid, which splits the output beams into transmitted and reflected components. The two polarizations are focussed onto two thermopile detectors; each consisting of a gold black foil welded to the top of two bismuth pyramids. The gold black is 30 microns thick, and the weld area is approximately 2 microns in diameter. The detectors are extremely fragile and the weld can be broken with a miniscule amount of airflow. The detectors consistently passed acoustic testing to qualification levels that simulated the launch environment of the Titan IV launch vehicle. However, they experienced a 50% failure rate when installed in the focal plane assembly during instrument level acoustic tests. A test focal plane was developed with small pressure transducers in the nominal detector locations. These tests indicated over 10 dB of acoustic amplification in the focal plane within the instrument during testing. New techniques were developed to allow testing of the focal plane without over testing the instrument, and modifications were made the focal plane assembly to successfully attenuate the amplification.

Hagopian, John G.↗

NASA NTRS2017

Utilizing the Precessing Orbit of TRMM to Produce Hourly Corrections of Geostationary Infrared Imager Data with the VIRS Sensor

Accurate characterization of the Earth's radiant energy is critical for many climate monitoring and weather forecasting applications. For example, groups at the NASA Langley Research Center rely on stable visible- and infrared-channel calibrations in order to understand the temporal/spatial distribution of hazardous storms, as determined from an automated overshooting convective top detection algorithm. Therefore, in order to facilitate reliable, climate-quality retrievals, it is important that consistent calibration coefficients across satellite platforms are made available to the remote sensing community, and that calibration anomalies are recognized and mitigated. One such anomaly is the infrared imager brightness temperature (BT) drift that occurs for some Geostationary Earth Orbit satellite (GEOsat) instruments near local midnight. Currently the Global Space-Based Inter-Calibration System (GSICS) community uses the hyperspectral Infrared Atmospheric Sounding Interferometer (IASI) sensor as a common reference to uniformly calibrate GEOsat IR imagers. However, the combination of IASI, which has a 21:30 local equator crossing time (LECT), and hyperspectral Atmospheric Infrared Sounder (AIRS; 01:30 LECT) observations are unable to completely resolve the GEOsat midnight BT bias. The precessing orbit of the Tropical Rainfall Measuring Mission (TRMM) Visible and Infrared Scanner (VIRS), however, allows sampling of all local hours every 46 days. Thus, VIRS has the capability to quantify the BT midnight effect observed in concurrent GEOsat imagers. First, the VIRS IR measurements are evaluated for long-term temporal stability between 2002 and 2012 by inter-calibrating with Aqua-MODIS. Second, the VIRS IR measurements are assessed for diurnal stability by inter-calibrating with Meteosat-9 (Met-9), a spin-stabilized GEOsat imager that does not manifest any diurnal dependency. In this case, the Met-9 IR imager is first adjusted with the official GSICS calibration coefficients. Then VIRS is used as a diurnal calibration reference transfer to produce hourly corrections of GEOsat IR imager BT. For the 9 three-axis stabilized GEO imagers concurrent with VIRS, the midnight effect increased the BT on average by 0.5 K (11 microns) and 0.4 K (12 microns), with a peak at approx.01:00 local time. As expected, the spin-stabilized GEOsats revealed a smaller diurnal temperature cycle (mostly < 0.2 K) with inconsistent peak hours.

Scarino, Benjamin↗

NASA NTRS2004

The Terrestrial Planet Finder and Darwin Missions

Both in the United States and in Europe, teams of scientists and engineers are exploring the feasibility of the Terrestrial Planet Finder (TPF) and Darwin missions, which are designed to search for Earth-like planets in the habitable zone of nearby stars. In the US, the TPF Science Working Group is studying four options - small (4m by 6 m primary mirror) and large (4m by 10 m primary mirror) coronagraphs for planet detection at visible wavelengths, and structurally connected and free-flyer interferometers at thermal infrared wavelengths. The US TPF-SWG is charged with selecting an option for NASA by the end of 2006. In Europe the Darwin Terrestrial Exo-planet Advisory Team (TE- SAT) is exploring the free-flyer interferometer option only at this time. I will discuss the vurtures and difficulties of detecting and characterizing extra-solar planets in both wavelength regions as well as some of the technical challenges and progress in the past year.

Danchi, William C.↗

NASA NTRSDate not supplied

TPSAS-NF1676L-10574-DND

The Infrared Atmospheric Sounding Interferometer (IASI) aboard of MetOP-A was successfully launched on 19 October 2006 and has been providing excellent data for more than 3 years. The IASI spectra can be converted into proxy data for the NPOESS Crosstrack Infrared Sounder (CrIS) through a rigorous mathematical transformation by taking into account of instrument characteristics of both the IASI and the CrIS. The 15-channel AMSU temperature sounder, and the 5-channel and Microwave Humidity Sounder (MHS) aboard of MetOP-A can be used to generate proxy data for the NPOESS Advanced Technology Mircrowave Sounder (ATMS). The CrIS and ATMS make up the Cross-track Infrared and Microwave Sounder Suite (CrIMSS). CrIMSS will primarily provide global temperature, moisture, and pressure profiles. We will describe the method used in generating the proxy data and show results of using the proxy data for evaluation of the NPOESS CrIMSS Environmental Data Record (EDR) retrieval algorithm.

Xu Liu↗

NASA NTRSDate not supplied

TPSAS-NF1676L-10898-DND

Xu Liu↗

NASA NTRS1971

Astronomical infrared spectroscopy with a Connes-type interferometer. II - Mars, 2500-3500 per cm

Mars IR spectra with Connes-type interferometer, noting atmospheric absorption and albedo drop due to surface water

Beer, R.↗

NASA NTRS1972

Astronomical infrared spectroscopy with a Connes-type interferometer. III Alpha Orionis, 2600 to 3450 per cm.

Analysis of recent spectra of alpha Ori in the 3 to 4 micron region at a resolving power of about 10,000, showing clear evidence of the delta v = 1 sequence of the rotation-vibration bands of OH. A detailed investigation of the rotational and vibrational populations suggests that the OH is close to being in LTE at an apparent temperature of 4100 plus or minus 200 K. An OH abundance of 1.2 x 10 to the 20th molecules per cu cm and upper limits for H2O and H super 35 Cl of 8 x 10 to the 18th and 8 x 10 to the 17th molecules per cu cm, respectively, are deduced. It is also deduced that the rms turbulence velocity in the region of OH line formation is 11.5 plus or minus 2 km/sec. The implications of these data on abundances in M supergiant atmospheres are discussed.

Beer, R.↗

NASA NTRS1976

A spherical lamellar grating interferometer for airborne astronomical observations of far infrared objects

A lamellar grating has been developed to be used for very far infrared observations on the airborne observatory. The design characteristics and performance during laboratory testing and initial observations of Jupiter at wavelengths between 50 and 500 microns are presented.

Pipher, J. L.↗

NASA NTRS2013

Error Consistency Analysis Scheme for Infrared Ultraspectral Sounding Retrieval Error Budget Estimation

Great effort has been devoted towards validating geophysical parameters retrieved from ultraspectral infrared radiances obtained from satellite remote sensors. An error consistency analysis scheme (ECAS), utilizing fast radiative transfer model (RTM) forward and inverse calculations, has been developed to estimate the error budget in terms of mean difference and standard deviation of error in both spectral radiance and retrieval domains. The retrieval error is assessed through ECAS without relying on other independent measurements such as radiosonde data. ECAS establishes a link between the accuracies of radiances and retrieved geophysical parameters. ECAS can be applied to measurements from any ultraspectral instrument and any retrieval scheme with its associated RTM. In this manuscript, ECAS is described and demonstrated with measurements from the MetOp-A satellite Infrared Atmospheric Sounding Interferometer (IASI). This scheme can be used together with other validation methodologies to give a more definitive characterization of the error and/or uncertainty of geophysical parameters retrieved from ultraspectral radiances observed from current and future satellite remote sensors such as IASI, the Atmospheric Infrared Sounder (AIRS), and the Cross-track Infrared Sounder (CrIS).

Zhou, Daniel K.↗

NASA NTRS2004

Upcoming and Future Missions in the Area of Infrared Astronomy: Spacecraft and Ground-based Observations

The IRIS instrument on the Voyager spacecrafts made major discoveries with regard to the giant planets, their moons and rings and paved the way for future infrared observations for planetary missions within our solar system. The CIRS instrument of Cassini with much greater spectral-spatial resolution and sensitivity than that provided by IRIS is now rapidly approaching the Saturnian system with orbit insertion on July 1, 2004, for which CIRS is expected to provide an order of magnitude advance beyond that provided by IRIS. The Mars program is also presently dominated by infrared observations in the near to mid-infrared spectral bands for missions such as Mars Global Surveyor and its TES instrument and Odyssey with its THEMIS instrument. In the case of Earth science we have such missions as TIMED, which makes infrared observations of the thermosphere using the SABER instrument. With the newly formed New Frontiers Program we have the opportunity for $650M missions such as Kuiper Belt-Pluto Explorer and Jupiter Polar Orbiter with Probes. Under the Flagship line, once per decade, we have the opportunity for $1B missions for which Europa is presently being considered; for this mission infrared measurements could look for hot spots within the maze of cracks and faults on Europa s surface. On Kuiper Belt- Pluto there is an imaging near-IR spectrometer called LEISA. Another mission on the horizon is Titan Orbiter Aerorover Mission (TOAM) for which there is planned a state-of-art version of CIRS called TIRS on the orbiter that will map out the atmospheric composition with unprecedented wavelength coverage and spectral-spatial resolution. This instrument will also provide temperature maps of the surface of Titan to look for hot spots where life may form. On the same mission there will be a descent imager on the Aerorover (i.e., balloon) similar to that provided by LEISA on the Pluto mission to provide compositional-topographical maps of Titan s surface. Other future mission will also be discussed. Improved thermal detectors could have important applications in solar physics, specifically in the detection of far-IR synchrotron emission from energetic electrons in solar flares. For infrared astronomy we have missions like SIRTF and JWST, which will cover the spectral range from near-IR to far-IR in the search and probing of both new and old planetary systems in our galaxy and the measurement of the most distant galaxies of our universe. SIRTF is scheduled to be launched in August 2003, while JWST will be launched next decade. Another mission is TPF, which will use interferometer techniques at infrared wavelengths to search for planetary systems beyond 2010. With regard to ground based telescopes we have, for example, the twin 10 meter Keck telescopes and the IRTF telescope at Mauna Kea. The Keck telescopes are presently using interferometer techniques. Over the next several decades there are plans for 50 meter to 200 meter telescopes providing near-IR to far-IR measurements with the eventual plan to combine all telescopes using interferometer techniques to provide unprecedented spectral-spatial resolution and sensitivity.

Sittler, E. C., Jr.↗

NASA NTRS2009

Surface Emissivity Retrieved with Satellite Ultraspectral IR Measurements for Monitoring Global Change

Surface and atmospheric thermodynamic parameters retrieved with advanced ultraspectral remote sensors aboard Earth observing satellites are critical to general atmospheric and Earth science research, climate monitoring, and weather prediction. Ultraspectral resolution infrared radiance obtained from nadir observations provide atmospheric, surface, and cloud information. Presented here is the global surface IR emissivity retrieved from Infrared Atmospheric Sounding Interferometer (IASI) measurements under "clear-sky" conditions. Fast radiative transfer models, applied to the cloud-free (or clouded) atmosphere, are used for atmospheric profile and surface parameter (or cloud parameter) retrieval. The inversion scheme, dealing with cloudy as well as cloud-free radiances observed with ultraspectral infrared sounders, has been developed to simultaneously retrieve atmospheric thermodynamic and surface (or cloud microphysical) parameters. Rapidly produced surface emissivity is initially evaluated through quality control checks on the retrievals of other impacted atmospheric and surface parameters. Surface emissivity and surface skin temperature from the current and future operational satellites can and will reveal critical information on the Earth s ecosystem and land surface type properties, which can be utilized as part of long-term monitoring for the Earth s environment and global climate change.

Zhou, Daniel K.↗

NASA NTRS2008

High Vertically Resolved Atmospheric State Revealed with IASI Single FOV Retrievals under All-weather Conditions

The Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp satellite was launched on October 19, 2006. The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25 cm(exp -1) and a spectral coverage from 645 to 2760 cm(exp -1). Ultra-spectral resolution infrared spectral radiance obtained from near nadir observations provide atmospheric, surface, and cloud property information. An advanced retrieval algorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. Preliminary retrievals of atmospheric soundings, surface properties, and cloud optical/microphysical properties with the IASI observations are obtained and presented. These retrievals are further inter-compared with those obtained from airborne FTS system, such as the NPOESS Airborne Sounder Testbed - Interferometer (NAST-I), dedicated dropsondes, radiosondes, and ground based Raman Lidar. The capabilities of satellite ultra-spectral sounder such as the IASI are investigated to benefit future NPOESS operation.

Zhou, Daniel K.↗

NASA NTRS1976

The measurement of carbon monoxide and methane in the national capital air quality control region. III - Correlation interferometer results

Two types of experiments were performed with a correlation interferometer on-board a Bell Jet Ranger 206 Helicopter. The first consisted of simultaneous ground- and air-truth measurements as the instrumented helicopter passed over the Cheverly site. The second consisted of several measurement flights in and around the national capital air quality control region (Washington, D.C.). The correlation interferometer data, the infrared Fourier spectrometer data, and the integrated altitude sampling data showed agreement within the errors of the individual measurements. High values for CO were found from the D.C. flight data to be reproducible and concentrated in areas of stop-and-go traffic. It is concluded, that pollutants at low altitudes are detectable from an air-borne platform by remote correlation interferometry and that the correlation interferometer measurements agree with ground- and air-truth data.

Goldstein, H. W.↗

NASA NTRSDate not supplied

Seasonal Surface Spectral Emissivity Derived From MODIS Data

Surface emissivity is essential for many remote-sensing applications including the retrieval of surface skin temperature from satellite-based infrared measurements, the determination of cloud detection thresholds, and the estimation of the surface longwave radiation emission, an important component of the energy budget of the surface-atmosphere interface. The CERES (Clouds and the Earth’s Radiant Energy System) Project is measuring broadband shortwave and longwave radiances and deriving cloud properties from the MODIS on Terra and Aqua and from the VIIRS on NOAA-19 and NOAA-20 orbiters to produce combined global radiation and cloud property data sets. Zhou et al. (IEEE Trans. Geosci. Remote Sens., 49, 2011) used Infrared Atmospheric Sounding Interferometer (IASI) data to create a high spectral resolution surface emissivity atlas for remote sensing and modeling applications. The IASI measures spectral radiances between 3.62 and 15.5 μm. The VIIRS I4 channel width is from 3.55 to 3.93 μm, while MODIS Band 20 is from 3.66 to 3.84 m. Comparisons of top-of-atmosphere (TOA) radiance calculations with MODIS and VIIRS observations for these bands relative to bands in the mid-infrared suggest that the IASI emissivity atlas near 3.7 µm may not be suitable for CERES cloud retrievals. In this paper, the IASI emissivities for the VIIRS and MODIS bands centered near 11m are used to derive surface skin temperature from nighttime MODIS/VIIRS data. The Goddard Earth Observing System for Instrument Teams (GEOS-IT) numerical weather analyses provide temperature and water vapor profiles fused to correct the observed radiances for atmospheric absorption and emission. Global seasonal emissivity maps are then derived for the VIIRS and MODIS 3.7-m bands that are consistent with the derived skin temperatures and the observed TOA radiances. These seasonal climatology maps are validated and will be used in CERES Edition 5 and other CERES-related cloud retrieval algorithms to provide improved clear-sky radiances and derived cloud properties.

Surface Emissivity↗

NASA NTRS2018

An Accurate Method for Correcting Spectral Convolution Errors in Intercalibration of Broadband and Hyperspectral Sensors

The intercalibration between a broadband and a hyperspectral satellite Earth observation system requires the convolution of the hyperspectral data with the spectral response functions (SRFs) of the corresponding broadband channels. There are two potential issues associated with the convolution procedure. First, the finite resolution of a hyperspectral spectrum, that is, the deviation from the highly accurate line-by-line monochromatic radiances, will contribute to convolution errors. The magnitude of the errors depends on the spectral resolution and the SRF shape of the hyperspectral instrument. This type of the convolution error has not been well recognized, and there is a lack of corresponding discussion in most published papers. Although it is small as compared with the instrument accuracy of existing hyperspectral sounders, the error is deemed to be signicant when it is compared with the stringent calibration requirement imposed by future climate missions like the Climate Absolute Radiance and Refractivity Observatory (CLARREO). Second, some broadband channels are insufficiently covered by the hyperspectral data, causing spectral gaps that lead to convolution errors. Although several methods have been developed to fill the spectral gaps and hence compensate for the second type of convolution error, the correction accuracy may still need improvement especially when a large spectral gap needs to be lled. This paper presents a methodology to accurately quantify and compensate for both types of convolution errors. This methodology utilizes the available hyperspectral information to correct the scene-dependent convolution errors due to either the limited spectral resolution or spectral gaps. We use simulations to characterize the intercalibration errors between the Moderate resolution Imaging Spectroradiometer (MODIS) and current operational infrared sounders. We demonstrate that convolution errors can be effectively removed to meet the highly accurate intersatellite calibration requirement proposed by the Climate Absolute Radiance and Refractivity Observatory. Our methodology is also validated using real satellite data for the intercalibration between Aqua MODIS and Aqua Atmospheric Infrared Sounders (AIRS). Our study demonstrates that the accurate characterization and correction for the convolution errors greatly reduces the scene-dependent and spectrally dependent errors, being critical to the consistency check between Infrared Atmospheric Sounding Interferometer (IASI) and AIRS using the double-difference method. The convolution correction also facilitates the evaluation for other intercalibration errors (e.g., the drift of MODIS SRFs). Our derived SRF shift values from MODIS-AIRS (after convolution error corrections) and from MODIS-IASI intercalibration are consistent with each other. We further extend the methodology to study the calibration of a broadband channel which is either completely or largely uncovered bya hyperspectral measurement.The large spectral gap-filling methodology is validated by demonstrating the accurate prediction of the MODIS radiance of band 29 using the Cross-track Infrared Sounder spectra, with the real IASI spectral data being used as the reference.

Correction Method↗

NASA NTRS2020

Comparison of the MODIS and VIIRS Thermal Emissive Band Radiometric Calibration

Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) are major instruments for Earth science observations.Nearly 40 MODIS scientific products and a wide range of VIIRS environmental data records are produced using their global observations. The consistency of the MODIS and VIIRS calibrated data is important for the study of Earth science. This article assesses the calibration consistency of the Aqua MODIS and VIIRS thermal emissive band (TEB) data. To remove the impact of the mismatched relative spectral response (RSR) on the comparisons, the simultaneous nadir observation data from the cross-track infrared sounder (CrIS) and the infrared atmospheric sounding interferometer (IASI) are used as references in two different methods to independently verify the consistency. The comparisons of the MODIS and VIIRS TEB calibrated data show that the brightness temperature (BT) differences for comparable bands between MODIS and VIIRS are in general within 0.2 K for BT larger than 230 K. The differences of all comparable MODIS and VIIRS TEBs are consistent over time. MODIS measurements agree better with N20 VIIRS than with Suomi National Polar-orbiting Partnership (S-NPP) VIIRS. The S-NPP VIIRS measurements are higher than N20 VIIRS, within 0.1 Kfor long-wave infrared (LWIR) bands and 0.3 K for band M13.

Calibration↗

NASA NTRS2002

Ultralow-Background Large-Format Bolometer Arrays

In the coming decade, work will commence in earnest on large cryogenic far-infrared telescopes and interferometers. All such observatories - for example, SAFIR, SPIRIT, and SPECS - require large format, two dimensional arrays of close-packed detectors capable of reaching the fundamental limits imposed by the very low photon backgrounds present in deep space. In the near term, bolometer array architectures which permit 1000 pixels - perhaps sufficient for the next generation of space-based instruments - can be arrayed efficiently. Demonstrating the necessary performance, with Noise Equivalent Powers (NEPs) of order 10-20 W/square root of Hz, will be a hurdle in the coming years. Superconducting bolometer arrays are a promising technology for providing both the performance and the array size necessary. We discuss the requirements for future detector arrays in the far-infrared and submillimeter, describe the parameters of superconducting bolometer arrays able to meet these requirements, and detail the present and near future technology of superconducting bolometer arrays. Of particular note is the coming development of large format planar arrays with absorber-coupled and antenna-coupled bolometers.

Benford, Dominic↗

NASA NTRS1998

Throughput of the Composite Infrared Spectrometer (CIRS) Mid Infrared (MIR) Channel for the Cassini Mission to Saturn

The Composite Infrared Spectrometer (CIRS) of the Cassini mission to Saturn has two interferometers covering the far infrared and mid infrared wavelength region. The instrument was aligned at ambient temperature, but operates at 170 Kelvin and has challenging interferometric alignment tolerances. Cryogenic alignment tests of the instrument indicate that it should suffer minimal degradation due to the cooldown from ambient to operational temperature. System level tests performed by the calibration team indicated a lower than expected signal level on the MIR channel, while providing ambiguous optical throughput data. Therefore it became imperative to develop a metric that could be used to determine the instrument performance at both the instrument and system levels, at ambient and cryogenic temperature. Modulation efficiency and throughput measurements were performed and new analytical models developed to evaluate the status of the instrument. Empirical and analytical data were eventually reconciled and deviations from the design values explained.

Hagopian, John G.↗