FIRESS is the multi-purpose spectrometer proposed for the PRobe far-Infrared Mission for Astrophysics (PRIMA). The sensitive spectrometer on the cold telescope provide factors of 1,000 to 100,000 improvement in spatial-spectral mapping speed relative to Herschel, accessing galaxies across the arc of cosmic history via their dust-immune far-infrared spectral diagnostics. FIRESS covers the 24 to 235 micron range with four slit-fed grating spectrometer modules providing resolving power between 85 and 130. The four slits overlap in pairs so that a complete spectrum of any object of interest is obtained in 2 pointings. For higher-resolving-power studies, a Fourier-transform module (FTM) is inserted into the light path in advance of the grating backends. The FTM serves all four bands and boosts the resolving power up to 4,400 at 112 microns, allowing extraction of the faint HD transition in protoplanetary disks. FIRESS uses four 2016-pixel arrays of kinetic inductance detectors (KIDs) which operate at the astrophysical photon background limit. KID sensitivities for FIRESS have been demonstrated, and environmental qualification of prototype arrays is underway.
PRIMA addresses questions about the origins and growth of planets, supermassive black holes, stars, and dust. Much of the radiant energy from these formation processes is obscured and only emerges in the far infrared (IR) where PRIMA observes (24–261 um). PRIMA’s PI science program (25% of its 5-year mission) focuses on three questions and feeds a rich archival Guest Investigator program: How do exoplanets form and what are the origins of their atmospheres? How do galaxies’ black holes and stellar masses co-evolve over cosmic time? How do interstellar dust and metals build up in galaxies over time? PRIMA provides access to atomic (C, N, O, Ne) and molecular lines (HD, H2O, OH), redshifted PAH emission bands, and far-IR dust emission. PRIMA’s 1.8-m, 4.5-K telescope serves two instruments using sensitive KIDs: the Far-InfraRed Enhanced Survey Spectrometer (continuous, high-resolution spectral coverage with over an order of magnitude improvement in spectral line sensitivity and 3-5 orders of magnitude improvement in spectral survey speed) and the PRIMA Imager (hyperspectral imaging, broadband polarimetry). PRIMA opens new discovery space with 75% of the time for General Observers.
PRIMA is a cryogenically-cooled, far-infrared observatory for the community for the beginning of the next decade (∼2031). It features two instruments, PRIMAger and FIRESS. The PRIMAger instrument will cover the mid-IR to far-IR wavelengths, from about 25 to 260 µm. Hyperspectral imaging can be obtained in 12 medium-resolution bands (R ∼ 10, more precisely a linear variable filter) covering the wavelength range from 25 to 80 micrometers, and broad-band (R ∼ 4) photometric and polarimetric imaging can be carried out in four bands between 80 and 260 µm. PRIMAger’s unique and unprecedented scientific capabilities will enable study, both in PI and GO programs, of black hole and star-formation coevolution in galaxies, the evolution of small dust grains over a wide range of redshift, and the effects of interstellar magnetic fields in various environments, as well as opening up a vast discovery space with its versatile imaging and polarimetric capabilities. One of the most ambitious possibilities is to carry out an all-sky far-IR survey with PRIMAger, creating a rich data set for many investigations. The design of PRIMAger is presented is an accompanying paper (Ciesla et al., SPIE Astronomical Telescopes + Instrumentation 2024).
We present a characterization of the mapping from resonant frequency to spatial position for a kilopixel kinetic inductance detector (KID) array developed for the Probe far-Infrared Mission for Astrophysics (PRIMA). This work targets the longest wavelength band of PRIMA’s FIRESS spectrometer, which in total spans 24 to 235 μm. Light emitting diodes arrayed to match repeating unit cells of 16 KIDs first discriminate among unit cells. Within each unit cell, frequencies are widely spaced, so positions are discriminated by theoretical predictions of the relative frequency spacing between detectors based on KID geometries. With this mapping, we analyze board features to improve the accuracy of modeling PRIMA KIDs and inform future fabrication runs.
KEYWORDS: Sensors, Mirrors, Optical filters, Black bodies, Signal to noise ratio, Readout integrated circuits, Multiplexers, Prototyping, Staring arrays, Temperature metrology
The Prototype Hyspiri-TIR (PHyTIR) instrument was developed under NASA’s instrument incubator program and is now operational in the laboratory. The scan head uses state-of-the-art focal plane technology to rapidly acquire data from an eight inch telescope focused at infinite, reflective relay and continuously rotating scan mirror. A series of narrowband interference filters are placed in close proximity to the focal plane. Arrays of 256×16 Mercury Cadmium detectors are under each filter. The detectors have their long wave cutoff at 13.2μm. The filters serve to block out unwanted radiation from other spectral channels, hence forming a high performance multi-band imager with the use of the scanning mirror.
The Astrophysics Focused Telescope Assets (AFTA) study in 2012-2013 included a high-contrast stellar coronagraph to complement the wide-field infrared survey (WFIRST) instrument. The idea of flying a coronagraph on this telescope was met with some skepticism because the AFTA pupil has a large central obscuration with six secondary mirror struts that impact the coronagraph sensitivity. However, several promising coronagraph concepts have emerged, and a corresponding initial instrument design has been completed. Requirements on the design include observations centered 0.6 deg off-axis, on-orbit robotic serviceability, operation in a geosynchronous orbit, and room-temperature operation (driven by the coronagraph’s deformable mirrors). We describe the instrument performance requirements, the optical design, an observational scenario, and integration times for typical detection and characterization observations.
The Jet Propulsion Laboratory is currently developing an end-to-end instrument which will provide a proof of concept prototype vehicle for a high data rate, multi-channel, thermal instrument in support of the Hyperspectral Infrared Imager (HyspIRI)–Thermal Infrared (TIR) space mission. HyspIRI mission was recommended by the National Research Council Decadal Survey (DS). The HyspIRI mission includes a visible shortwave infrared (SWIR) pushboom spectrometer and a multispectral whiskbroom thermal infrared (TIR) imager. The prototype testbed instrument addressed in this effort will only support the TIR. Data from the HyspIRI mission will be used to address key science questions related to the Solid Earth and Carbon Cycle and Ecosystems focus areas of the NASA Science Mission Directorate. Current designs for the HyspIRI-TIR space borne imager utilize eight spectral bands delineated with filters. The system will have 60m ground resolution, 200mK NEDT, 0.5C absolute temperature resolution with a 5-day repeat from LEO orbit. The prototype instrument will use mercury cadmium telluride (MCT) technology at the focal plane array in time delay integration mode. A custom read out integrated circuit (ROIC) will provide the high speed readout hence high data rates needed for the 5 day repeat. The current HyspIRI requirements dictate a ground knowledge measurement of 30m, so the prototype instrument will tackle this problem with a newly developed interferometeric metrology system. This will provide an absolute measurement of the scanning mirror to an order of magnitude better than conventional optical encoders. This will minimize the reliance on ground control points hence minimizing post-processing (e.g. geo-rectification computations).
The Jet Propulsion Laboratory is currently developing an end-to-end instrument which will provide a proof of concept
prototype vehicle for a high data rate, multi-channel, thermal instrument in support of the Hyperspectral Infrared Imager
(HyspIRI)-Thermal Infrared (TIR) space mission. HyspIRI mission was recommended by the National Research
Council Decadal Survey (DS). The HyspIRI mission includes a visible shortwave infrared (SWIR) pushboom
spectrometer and a multispectral whiskbroom thermal infrared (TIR) imager. The prototype testbed instrument
addressed in this effort will only support the TIR. Data from the HyspIRI mission will be used to address key science
questions related to the Solid Earth and Carbon Cycle and Ecosystems focus areas of the NASA Science Mission
Directorate. Current designs for the HyspIRI-TIR space borne imager utilize eight spectral bands delineated with filters.
The system will have 60m ground resolution, 200mK NEDT, 0.5C absolute temperature resolution with a 5-day repeat
from LEO orbit. The prototype instrument will use mercury cadmium telluride (MCT) technology at the focal plane
array in time delay integration mode. A custom read out integrated circuit (ROIC) will provide the high speed readout
hence high data rates needed for the 5 day repeat. The current HyspIRI requirements dictate a ground knowledge
measurement of 30m, so the prototype instrument will tackle this problem with a newly developed interferometeric
metrology system. This will provide an absolute measurement of the scanning mirror to an order of magnitude better
than conventional optical encoders. This will minimize the reliance on ground control points hence minimizing postprocessing
(e.g. geo-rectification computations).
The NASA Jupiter Europa Orbiter (JEO) conceptual payload contains a thermal instrument with six different spectral
bands ranging from 8μm to 100μm. The thermal instrument is based on multiple linear arrays of thermopile detectors
that are intrinsically radiation hard; however, the thermopile CMOS readout needs to be hardened to tolerate the
radiation sources of the JEO mission. Black Forest Engineering is developing a thermopile readout to tolerate the JEO
mission radiation sources. The thermal instrument and ROIC process/design techniques are described to meet the JEO
mission requirements.
Thermal detectors, while typically less sensitive than quantum detectors, are useful when the combination of long wavelength signals and relatively high temperature operation makes quantum detectors unsuitable. Thermal detectors are also appropriate in applications requiring flat spectral response over a broad wavelength range. JPL produces thermopile detectors and linear arrays to meet space science requirements in these categories. Thermopile detectors and arrays are currently being fabricated for two space applications. The first is the Mars Climate Sounder (MCS) instrument, to fly on the Mars Reconnaissance Orbiter mission, scheduled to launch in 2005. MCS is an atmospheric limb sounder utilizing nine 21-element thermopile arrays. The second application is the Earth Radiation Budget Suite (ERBS), part of the National Polar Orbiting Environmental Satellite System (NPOESS). This instrument measures upwelling radiation from the earth in the spectral range 0.3-100 μm.
KEYWORDS: Sensors, Thermoelectric materials, Bolometers, Information operations, Performance modeling, Scanning electron microscopy, Temperature metrology, Night vision, Multiplexing, Imaging arrays
Thermopiles are uncooled, broadband detectors that require no chopper or temperature stabilizer. Their wide operating- temperature range, lack of temperature stabilization, and radiometric accuracy make thermopiles well suited for some space-based scientific imaging applications. These detectors may also offer advantages over bolometers for night vision. Previous work at JPL has produced thermopile linear arrays with D* values over 109 cmHz1/2/W by combining high- performance thermoelectric materials Bi-Te and Bi-Sb-Te with bulk micromachining processes. To date, however, 2-D thermopile arrays have demonstrated only moderate performance. The purpose of the present work is to improve thermopile 2-D arrays substantially by combining Bi-Te and Bi-Sb-Te thermoelectric materials with a unique pixel structure and low-noise readout circuitry. The initial goal is a 128 X 128 array with a single multiplexed analog output stream, with system D* values (including readout noise) of 109 cmHz1/2/W, and with a focal-plane power dissipation of 20 mW. 100 micrometers square detectors have been demonstrated with D* values of 2 X 108 cmHz1/2/W and response times of 4 ms. Models predict D* values well over 109 cmHz1/2/W for optimized detectors. Modeling of a preliminary readout design shows that, for the expected detector resistance of 100 kΩ, the total noise will be 50% higher than the detector Johnson noise. CMOS test chips containing front-end circuits presently display a noise about 2.5 times higher than modeled and a power dissipation of 0.6 μW per pixel.
The temperature stabilization requirements of unchopped thermistor bolometers and thermopile detectors are analyzed. The detector temperature, on which the bolometer output signal depends, is quite sensitive to changes in instrument temperature but relatively insensitive to changes in scene temperature. In contrast, the difference in temperature between detector and substrate, on which the thermopile signal depends, is equally sensitive to changes in instrument and scene temperature. Expressions for these dependencies are derived based on a simplified instrument model. It is shown that for a typical uncooled thermal imager, the temperature stabilization requirements for a bolometer are tow orders of magnitude more stringent than those for a thermopile detector.
Linear thermopile infrared detector arrays have been produced with D* values as high as 2.2 X 109 cmHz1/2W for 83 ms response times. Typical responsivity is 1000 V/W. This result has been achieved with Bi-Te and Bi-Sb-Te thermoelectric materials on micromachined silicon nitride membranes. Results for several device geometries are described and compared to literature values for Schwartz type thermocouple detectors and for thin film thermopile detectors and arrays. Measurements of responsivity as a function of modulation frequency and wavelength are presented.
Single detectors and linear arrays of microbolometers utilizing the superconducting transition edge of YBa2Cu3O7 have been fabricated by micromachining on silicon wafers. A D* of 8 +/- 2 X 109 cm Hz1/2/watt has been measured on a single detector. This is the highest D* reported on any superconducting microbolometer operating at temperatures higher than about 70 K. The NEP of this device was 1.5 X 10-12 watts/HzHLF at 2 Hz, at a temperature of 80.7 K. The thermal time constant was 105 msec, and the detector area was 140 micrometers X 105 micrometers . The use of batch silicon processing makes fabrication of linear arrays of these detectors relatively straightforward. The measured responsivity of detectors in one such array varied by less than 20% over the 6 mm length of the 64-element linear array. This measurement shows that good uniformity can be achieved at a single operating temperature in a superconductor microbolometer array, even when the superconducting resistive transition is a sharp function of temperature. The thermal detection mechanism of these devices gives them broadband response. This makes them especially useful at long wavelengths (e.g. (lambda) > 20 micrometers ), where they provide very high sensitivity at relatively high operating temperatures.
Superconducting transition-edge infrared microbolometers have been fabricated by silicon micromachining using an epitaxial YLa.05Ba1.95Cu3O7-x (YBCO) film on a epitaxial yttria-stabilized zirconia buffer layer on silicon. The low thermal conductance of the micromachined structures combined with the sharp resistance change at the superconducting transition results in very sensitive infrared detectors. The broadband response of these thermal detectors makes them particularly useful at wavelengths longer than the typical operating range of semiconductor detectors ((lambda) greater than about 20 micrometers ) at moderately high temperatures (T approximately 70 K and higher). The use of standard silicon processing promises low-cost monolithic integration of the readout electronics for arrays of these devices. Preliminary measurements are reported here on a device 140 micrometers X 105 micrometers in size with a detectivity, D*, of 8 +/- 2 X 109 cm Hz1/2/Watt, and NEP of 1.5 X 10-12 Watts/Hz1/2 at 2 Hz and 80.7 K. This value of D* exceeds the highest previously reported D* for a YBCO transition-edge bolometer, and is comparable to the highest reported D* for a thermal detector operating at greater than about 70 K. The thermal time constant for this device was 105 +/- 20 msec.
High frequency detector and circuit applications often require device fabrication on medium-to-low dielectric constant substrates ((epsilon) < 12). Silicon-on-sapphire (SOS) substrates have acceptably low dielectric constants and provide other important advantages, including the possibility of monolithic integration of silicon and superconducting circuitry. Our initial results with YBa2Cu3O7-x(YBCO) edge- geometry superconductor/normal-metal/superconductor (SNS) weak links fabricated on r-plane SOS substrates using cubic zirconia (YSZ) buffer layers revealed problems with grain boundary nucleation in the YBCO counterelectrode. These results motivated development of a new multilayer buffer system consisting of an epitaxial YSZ film grown on an SOS substrate, overlaid by a thin YBCO 'seed' layer, and an epitaxial SrTiO3 (STO) layer. STO - YBCO bilayers grown over the YBCO seed layer show a remarkable improvement in epitaxial quality and in YBCO electrical properties relative to similar bilayers grown directly on the YSZ buffer. In addition, SNS weak links fabricated on SOS substrates using the multilayer buffer system exhibit dramatically improved electrical characteristics compared to devices produced on YSZ buffer layers. These are the first epitaxial edge-geometry SNS weak links produced on SOS substrates.
High-temperature superconducting staring arrays are potentially important for both space and terrestrial applications which require the combination of high sensitivity over a broad wavelength range and relatively high temperature operation. In many such array applications sensitivity is more important than speed of response. Thus, it is desirable to design low- thermal-mass pixels that are thermally isolated from the substrate. To this end, Johnson, et al. at Honeywell have fabricated meander lines of YBa2Cu3O7-x (YBCO) sandwiched between layers of silicon nitride on silicon substrates. The silicon was etched out from under each YBCO meander line to form low-thermal-mass, thermally isolated microbolometers. These 125 micrometers X 125 micrometers devices are estimated to have a noise equivalent power of 1.1 X 10-12 W/Hz1/2 near 5 Hz with a 5 (mu) A bias (neglecting contact noise). A drawback of this original Honeywell design is that the YBCO is grown on an amorphous silicon nitride underlayer, which precludes the possibility of epitaxial YBCO growth. The YBCO therefore has a broad resistive transition, which limits the bolometer response, and the grain boundaries lead to excess noise. We discuss the potential performance improvement that could be achieved by using epitaxial YBCO films grown on epitaxial yttria-stabilized zirconia buffer layers on silicon. This analysis shows a significant signal to noise improvement at all frequencies in devices incorporating epitaxial YBCO films. Progress toward fabricating such devices is discussed.
Hamid Javadi, Jeff Barner, Javier Bautista, Kul Bhasin, J. Bowen, Wilbert Chew, Chris Chorey, Marc Foote, B. Fujiwara, A. Guern, Brian Hunt, Regis Leonard, Gerry Ortiz, Daniel Rascoe, Robert Romanofsky, Richard Vasquez, Paul Wamhof
A low-noise microwave receiver downconverter utilizing thin-film high-critical-temperature superconducting (HTS) passive circuitry and semiconductor active devices has been developed for use in space. It consists of an HTS pre-select filter, a cryogenic low-noise amplifier, a cryogenic mixer, and a cryogenic oscillator with an HTS resonator. The downconverter converts a 200 MHz wide band centered around 7.35 GHz to a band centered around 1.0 GHz. When cooled to 77 K, the downconverter plus cables inside a cryogenic refrigerator produced a noise temperature measured at the refrigerator port of approximately 50 K with conversion gain of 18 dB.
Thin film low-pass microwave filters have been made with laser-ablated YBa2Cu3O(7-delta) (YBCO) deposited on LaAlO3 substrates, using a coplanar waveguide structure. The coplanar waveguide sections had dimensions suited for integrated circuits. Measured losses in liquid nitrogen were superior to the loss in a similar thin-film copper filter throughout the 0 to 9.5 GHz pass-band. A simple transmission-line model is adequate for filter design using YBCO films with repeatable characteristics. The measured filters demonstrate the performance of fully patterned YBCO after sealing in space-qualifiable hermetic packages. Five packaged filters of this design were delivered to the Naval Research Laboratory as candidates for space flight in the High Temperature Superconductivity Space Experiment.
We describe the fabrication and characterization of superconductor/normal metal/superconductor (SNS) devices made with the high-temperature superconductor (HTS) YBa2Cu3O(7-x). Structures of YBa2Cu3O(7-x)/Au/Nb on c-axis-oriented YBa2Cu3O(7-x) were made in both sandwich and edge geometries in order to sample the HTS material both along and perpendicular to the conducting a-b planes. These devices display fairly ideal Josephson properties at 4.2 K. In addition, devices consisting of YBa2Cu3O(7-x)/YBa2Cu3O(y)/YBa2Cu3O(7-x), with a 'normal metal' layer of reduced transition temperature YBa2Cu3O(7-x) were fabricated and show a great deal of promise for applications near 77 K. Current-voltage characteristics like those of the Resistively-Shunted Junction model are observed, with strong response to 10 GHz radiation above 60 K.
Fabrication and testing of planar and edge geometry YBaCuO/Au/Nb superconductor/normal-metal/superconductor (SNS) device structures is described. Weak-link devices of this type serve as sensitive probes of the electrical quality of the YBaCuO/Au interface. The devices are fabricated using laser-ablated, in situ, c-axis-oriented YBaCuO thin films, with both annealed and unannealed YBaCuO/Au interfaces. The planar SNS structures are formed by sequential, in situ deposition of YBaCuO, Au, and Nb, followed by etching, planarization, and wiring electrode definition to produce junctions ranging from 5 to 20 micron on a side. Resulting RnA products are 1-10 x 10 to the -8th ohm-sq cm with critical current densities up to 5 kA/sq cm. For the edge geometry devices, the YBaCuO film edges are patterned using Ar ion milling, followed by a low energy ion cleaning step and in situ deposition of Au and Nb. Devices with areas in the 10 to the -7th to 10 to the -8th sq cm range have been fabricated with RnA products lower than 10 to the -8th ohm-sq cm and critical current densities up to 3kA/sq cm. Both types of devices show ac Josephson steps under microwave irradiation. The best results have been obtained with annealed YBaCuO/Au interfaces.
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