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Circuit provides dual function of frequency discriminator/phase detector which reduces frequency acquisition time without adding to circuit complexity. Both frequency discriminators, in evaluated frequency discriminator/phase detector circuits, are effective two decades above and below center frequency.
The Gamma Ray Imaging Spectrometer (GRIS) was flown twice from Alice Springs, Australia, in the spring of 1992 for a total of 32 hr at float altitude. One of the seven Ge detectors was isotopically enriched (greater than 97% Ge-70). This was the first time an enriched-Ge detector was used for astrophysical observations. Because of its thick anticoincidence shield, the GRIS instrument background is dominated by internal beta-decay in the energy range of 200-1000 keV. Half of the contribution in this beta-decay 'hump' is due to neutron-activated Ge-74. In this energy range, GRIS observed a factor of 2 reduction in the background in the enriched detector, as predicted. In future instruments (e.g., INTEGRAL), with thicker anticoincidence shields and smaller apertures, the background reduction will be even larger. Three strong instrumental background lines (54, 67, and 139 keV) are also eliminated. The elimination of the first two is particularly important for cylotron line observations.
The EBIT Calorimeter Spectrometer (ECS) has recently been completed and is currently being installed at the EBIT facility at the Lawrence Livermore National Laboratory. The ECS will replace the smaller XRS/EBIT spectrometer that has been in almost continuous operation since 2000. The XRS/EBIT was based on a spare laboratory cryostat and an engineering model detector system from the Suzaku/XRS observatory. The new ECS spectrometer was built from the ground up to be a low maintenance, high performance microcalorimeter spectrometer with 4 eV resolution at 6 keV, 32 detector channels, 10 us event timing, and capable of uninterrupted acquisition sessions of over 70 hours at 50 mK. The XRSIEBIT program has been extremely successful, producing over two-dozen refereed publications on topics such as laboratory astrophysics, atomic physics, nuclear physics, and calibration of the spectrometers for the National Ignition Facility, with many more publications in preparation. The ECS spectrometer will continue this work into the future with improved spectral resolution, integration times, and ease-of-use. We designed the ECS instrument with TES detectors in mind by using the same highly successful magnetic shielding as our laboratory TES cryostats. This design will lead to a future TES instrument at the LLNL EBIT. This proposed future instrument would include a hybrid detector system with 0.8 eV resolution in the band from 0.1-1.0 keV, 2 eV from 0.1-10 keV, and 30 eV from 0.5-100 keV, with high quantum efficiency in each band. Here we discuss the legacy of the XRS/EBIT program, the performance of the new ECS spectrometer, and plans for a future TES spectrometer.
Multichroic polarization sensitive detectors enable increased sensitivity and spectral coverage for observations of the cosmic microwave background. An array optimized for dual frequency detectors can provide 1.7 times gain in sensitivity compared to a single frequency array. We present the design and measurements of horn coupled multichroic polarimeters encompassing the 90 and 150 GHz frequency bandsand discuss our plans to field an array of these detectors as part of the ACTPol project.
A ground based lightning detection system employs a grid of sensors, which record and evaluate the electromagnetic signal produced by a lightning strike. Several detectors gather information on that signal s strength, time of arrival, and behavior over time. By coordinating the information from several detectors, an event solution can be generated. That solution includes the signal s point of origin, strength and polarity. Determination of the location of the lightning strike uses algorithms based on long used techniques of triangulation. Determination of the event s original signal strength relies on the behavior of the generated magnetic field over distance and time. In general the signal from the event undergoes geometric dispersion and environmental attenuation as it progresses. Our knowledge of that radial behavior together with the strength of the signal received by detecting sites permits an extrapolation and evaluation of the original strength of the lightning strike. It also limits the detection efficiency (DE) of the network. For expansive grids and with a sparse density of detectors, the DE varies widely over the area served. This limits the utility of the network in gathering information on regional lightning strike density and applying it to meteorological studies. A network of this type is a grid of four detectors in the Rondonian region of Brazil. The service area extends over a million square kilometers. Much of that area is covered by rain forests. Thus knowledge of lightning strike characteristics over the expanse is of particular value. I have been developing a process that determines the DE over the region [3]. In turn, this provides a way to produce lightning strike density maps, corrected for DE, over the entire region of interest. This report offers a survey of that development to date and a record of present activity.
For high photon-efficiency deep space or low power optical communications links, such as the Orion Artemis-2 Optical Communications System (O2O) project, the received optical signal is attenuated to the extent that single- photon detectors are required. For direct-detection receivers operating at 1.55 µm wavelength, single-photon detectors including Geiger-mode InGaAs avalanche photon diodes (APDs), and in particular superconducting nanowire single-photon detectors (SNSPDs) offer the highest sensitivity and fastest detection speeds. However, these photon detectors exhibit a recovery time between registered input pulses, effectively reducing the detection efficiency over the recovery interval, resulting in missed photon detections, reduced count rate, and ultimately limiting the achievable data rate. A method to overcome this limitation is to divide the received optical signal into multiple detectors in parallel. Here we analyze this approach for a receiver designed to receive a high photon efficiency serially concatenated pulse position modulation (SCPPM) input waveform. From measured count rate and efficiency data using commercial SNSPDs, we apply a model from which we determine the effective detection efficiency, or blocking loss, for different input signal rates. We analyze the scalability of adding detectors in parallel for different modulation orders and background levels to achieve desired data rates. Finally we show tradeoffs between the number of detectors and the required received optical power, useful for real link design considerations.
The Roman Space Telescope (RST) Wide Field Instrument (WFI) will be utilizing a preliminary Science Data Processing (SDP) pipeline during its Integration and Test, and to some extent during Operations, to track basic statistics and identify known features such as cosmic rays, snowballs as well as possible anomalies in raw detector data. In our detectors, these anomalies appear as jumps in the ramp of a readout and are classified as cosmic rays if they appear as a streak or snowballs if they’re more circular. The WFI employs an array of 18 H4RG-10 detectors that collect image samples. Each set of raw frames within a non-destructive exposure is packaged by the SDP pipeline into image cubes for each detector. Each cube is a time series of 4096 × 4096 accumulating pixel frames. The preliminary analysis pipeline is used to locate anomalies in these time-series accumulation frames and identify the type of anomaly, either natural phenomena or detector characteristic. To compare different methods, we’ve implemented both heuristic-based and data-driven methods to identify anomalies. For the heuristic-based approach, we identify snowballs and cosmic rays by the size and shape of outlier pixel clusters between consecutive frames. For data driven methods, we evaluated a Convolutional Neural Network (CNN) model, and more traditional methods like Principal Component Analysis (PCA). CNN is a supervised learning/classification method. Thus, we used a labeled dataset of anomalies to perform segmentation of the image and identify anomalies. We used previously identified cosmic rays and snowballs to measure the accuracy and efficiency of the mentioned approaches. In evaluating these methods, we aim to pick the best fit for the SDP pipeline’s anomaly detection in terms of both performance and runtime.
The article describes the X-ray detector which will provide second-of-arc images for the HEAO-B X-ray observatory. The instrument uses microchannel plates as a photocathode surface and imaging photoelectron multiplier, and a crossed wire grid as a two-dimensional position-sensitive detector. Position determination is accomplished by electronic interpolation between the coarse grid wires. The detector provides the arrival time and position of each event which occurs within its field of view. Measurements of the spatial resolution (15 microns), temporal resolution (7.8 microsec), image distortion (less than 10 microns), uniformity of efficiency (less than plus or minus 10%), dark counting rate (0.2 cts/sq cm/s), and quantum efficiency (10% at 1.54 keV) of this detector are described. A summary of the procedure which was found useful during the initial turn-on of microchannel plates is given.
The design and operation of a 32 x 1 10 to the 15th power sq m array of scintillation detectors for the detection of 10 to the 15th power eV cosmic rays is described with an expected angular resolution of 1 deg, thus improving the present signal/background ratio for gamma ray sources. Data are recorded on a hybrid CAMAC, an in-house system which uses a laser and Pockel-Cell arrangement to routinely calibrate the timing stability of the detectors.
A coherent 1-micron Nd:YAG lidar system is employed to measure directly the reduced spatial coherence length rho 0 of the lidar returns caused by atmospheric turbulence. The experiments were conducted by using a 2 x 2 heterodyne detector array, which permitted real-time spatial correlation measurements of the lidar returns at two different detector spacings. The spatial correlation coefficients and spatial coherence length of the lidar returns from a hard target were measured during a day-to-night time period when the atmospheric turbulence parameter, Cn-squared, was measured to vary from 2 x 10 exp -13 to 2 x 10 exp -4 m exp -2/3. These directly measured values of rho 0 as a function of Cn-squared were found to be in good agreement with theoretical predictions.
A knowledge of the composition of planets, satellites, and asteroids is of primary importance in understanding the formation and evolution of the solar system. Gamma-ray spectroscopy is capable of measuring the composition of meter-depth surface material from orbit around any body possessing little or no atmosphere. Measurement sensitivity is determined by detector efficiency and resolution, counting time, and the background flux while the effective spatial resolution depends upon the field-of-view and counting time together with the regional contrast in composition. The advantages of using germanium as a detector of gamma rays in space are illustrated experimentally and a compact instrument cooled by passive thermal radiation is described. Calculations of the expected sensitivity of this instrument at the Moon and Mars show that at least a dozen elements will be detected, twice the number which have been isolated in the Apollo gamma-ray data.
A knowledge of the composition of planets, satellites, and asteroids is of primary importance in understanding the formation and evolution of the solar system. Gamma-ray spectroscopy is capable of measuring the composition of meter-depth surface material from orbit around any body possessing little or no atmosphere. Measurement sensitivity is determined by detector efficiency and resolution, counting time and the background flux, while the effective spatial resolution depends upon the field-of-view and counting time together with the regional contrast in composition. The advantages of using germanium as a detector of gamma rays in space are illustrated experimentally and a compact instrument cooled by passive thermal radiation is described. Calculations of the expected sensitivity of this instrument at the moon and Mars show that at least a dozen elements should be measurable, twice the number which have been isolated in the Apollo gamma-ray data
The EXIST active shields, now being planned for the main detectors of the coded aperture telescope, will have approximately 15 times the area of the BATSE detectors; and they will have a good geometry on the spacecraft for viewing both the leading and training Earth's limb for occultation observations. These occultation observations will complement the imaging observations of EXIST and can extend them to higher energies. Earth occultatio observations of the hard X-ray sky with BATSE on the Compton Gamma Ray Observatory developed and demonstrated the capabilities of large, flat, uncollimated detectors for this method. With BATSE, a catalog of 179 X-ray sources was monitored twice every spacecraft orbit for 9 years at energies above about 25 keV, resulting in 83 definite detections and 36 possible detections with 5-sigma detection sensitivities of 3.5-20 mcrab (20-430 keV) depending on the sky location. This catalog included four transients discovered with this technique and many variable objects (galactic and extragalactic). This poster will describe the Earth occultation technique, summarize the BATSE occultation observations, and compare the basic observational parameters of the occultation detector elements of BATSE and EXIST.
We are recovering the original telemetry (Figure I) from the Apollo Dust, Thermal, Radiation Environment Monitor (DTREM) experiment, more commonly known as the Dust Detector, and producing full time resolution (54 second) data sets for release through the Planetary Data System (PDS). The primary objective of the experiment was to evaluate the effect of dust deposition, temperature, and radiation damage on solar cells on the lunar surface. The monitor was a small box consisting of three solar cells and thermistors mounted on the ALSEP (Apollo Lunar Surface Experiments Package) central station. The Dust Detector was carried on Apollo's 11, 12, 14 and 15. The Apollo 11 DTREM was powered by solar cells and only operated for a few months as planned. The Apollo 12, 14, and 15 detectors operated for 5 to 7 years, returning data every 54 seconds, consisting of voltage outputs from the three solar cells and temperatures measured by the three thermistors. The telemetry was received at ground stations and held on the Apollo Housekeeping (known as "Word 33") tapes. made available to the National Space Science Data Center (NSSDC) by Yosio Nakamura (University of Texas Institute for Geophysics). We have converted selected parts of the telemetry into uncalibrated and calibrated output voltages and temperatures.
BATSE, one of four experiments on the Gamma Ray Observatory (GRO), is expected to provide the most sensitive observations of gamma-ray bursts yet obtained, as well as to provide long-term monitoring of hard X-ray and low-energy gamma-ray emission from bright pulsating sources, transients, and solar flares. Eight uncollimated modules, positioned at the corners of the spacecraft to provide an unobstructed view of the sky, detect sources by various techniques based on time variability. Use of detectors with anisotropic response allows location of gamma-ray bursts to be determined to an accuracy of about 1 deg using BATSE data alone. The completed BATSE underwent intensive testing and calibration prior to its delivery in October 1988.
The results of passive and active radiation measurements on Spacelab-1 are reported. Spacelab-1 was flown on the STS-9 mission, orbited at an altitude of 241 km, with an inclination of 57 deg and 240 hours of flight time. Approximately thirty passive detectors deployed inside the module, in the access tunnel, and outside on the pallet made possible the radiation measurements. The various forms of radiation measured were a low linear energy transfer component ranging from 94 to 133 mrads inside the module (average dose rate of 10.0 mrads/day; about twice the rate of earlier shuttle flights), an average mission dose-equivalent rate of about 18.5 mrem/day (six times higher than earlier flights), accumulated doses of 125 and 128 mrads and a yield of 17 and 12 mrads for passages through the South Atlantic Anomaly. Spacelab-1, because of its low altitude and short duration, was relatively benign in terms of total radiation dose. Some of the measurements such as high-LET particles and neutrons have biological significance and potential effects on future experiments.
A circuit for scanning and outputting the induced charges in a solid state charge coupled device (CCD) image detector is disclosed in an image detection system for use in a spacecraft attitude control system. The image detection system includes timing control circuitry for selectively controlling the output of the CCD detector so that video outputs are provided only with respect to induced charges corresponding to predetermined sensing element lines of the CCD detector. The timing control circuit and the analog to digital converter are controlled by a programmed microprocessor which defines the video outputs to be converted and further controls the timing control circuit so that no video outputs are provided during the delay associated with analog to digital conversion.
This paper examines the error resulting from using a lineal energy spectrum to represent a linear energy transfer spectrum for applications in the space radiation environment. Lineal energy and linear energy transfer spectra are compared in three diverse but typical space radiation environments. Different detector geometries are also studied to determine how they affect the error. LET spectra are typically used to compute dose equivalent for radiation hazard estimation and single event effect rates to estimate radiation effects on electronics. The errors in the estimations of dose equivalent and single event rates that result from substituting lineal energy spectra for linear energy spectra are examined. It is found that this substitution has little effect on dose equivalent estimates in interplanetary quiet-time environment regardless of detector shape. The substitution has more of an effect when the environment is dominated by solar energetic particles or trapped radiation, but even then the errors are minor especially if a spherical detector is used. For single event estimation, the effect of the substitution can be large if the threshold for the single event effect is near where the linear energy spectrum drops suddenly. It is judged that single event rate estimates made from lineal energy spectra are unreliable and the use of lineal energy spectra for single event rate estimation should be avoided.