The Star-Planet Activity Research CubeSat (SPARCS) is 6U CubeSat whose mission will be to observe low-mass stars in two ultraviolet (UV) bands. SPARCS will provide time-dependent spectral slope, intensity, and evolution of stellar radiation with the goal of understanding the short- and long-term variability of these targets.
Here we summarize the performance of SPARCam, the science camera for SPARCS. SPARCam is a two-detector camera system allowing independent commanding of two delta-doped, UV CCD47-20 detectors, separately optimized for the SPARCS near UV (NUV) and far UV (FUV) bands. The manuscript includes an overview of the UV detectors optimization and performance as well as a brief description of the camera electronics.
SPARCam was developed by the Jet Propulsion Laboratory and delivered to Arizona State University in October 2023.
We present an overview of the recent progress made in the development of a far-IR array of ultrasensitive hot-electron
nanobolometers (nano-HEB) made from thin titanium (Ti) films. We studied electrical noise, signal and noise
bandwidth, single-photon detection, optical noise equivalent power (NEP), and a microwave SQUID (MSQUID) based
frequency domain multiplexing (FDM) scheme. The obtained results demonstrate the very low electrical NEP down to
1.5×10-20 W/Hz1/2 at 50 mK determined by the dominating phonon noise. The NEP increases with temperature as ~ T3
reaching ~ 10-17 W/Hz1/2 at the device critical temperature TC = 330-360 mK. Optical NEP = 8.6×10-18 W/Hz1/2 at 357
mK and 1.4×10-18 W/Hz1/2 at 100 mK respectively, agree with thermal and electrical data. The optical coupling
efficiency provided by a planar antenna was greater than 50%. Single 8-μm photons have been detected for the first time
using a nano-HEB operating at 50-200 mK thus demonstrating a potential of these detectors for future photon-counting
applications in mid-IR and far-IR. In order to accommodate the relatively high detector speed (~ μs at 300 mK, ~ 100 μs
at 100 mK), an MSQUID based FDM multiplexed readout with GHz carrier frequencies has been built. Both the readout
noise ~ 2 pA/Hz1/2 and the bandwidth > 150 kHz are suitable for nano-HEB detectors.
In this paper we present the methodology for making absolute quantum efficiency (QE) measurements from the vacuum
ultraviolet (VUV) through the near infrared (NIR) on delta-doped silicon CCDs. Delta-doped detectors provide an
excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for
measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other
things, the use of a vacuum monochromator, and good camera vacuum to prevent chip condensation, and more stringent
handling requirements. The system used for these measurements was originally designed for deep UV characterization
of CCDs for the WF/PC instrument on Hubble and later for Cassini CCDs.
A novel predictive controller framework is discussed for integrated smart sensing and resource management in a distributed intelligent sensor network with sensor nodes whose useful active lifetime is significantly shorter than the required lifetime of the sensor system. Past sensor network research has focused on security and communication, but largely ignored the overall dynamic resource management issue of such distributed systems. Our contribution is in integrated control optimization and resource management algorithms to ensure proper functioning of distributed sensors in extremely limited
bandwidth, power, and storage. In this paper, we present a novel genetic algorithm (GA) for real-time system control and resource management that handles multiple conflicting objectives and constraints in the distributed system. We suggest using a GA-based predictive controller to give optimal actions that account for future states and future possible events while estimating the optimal control action policy. Our framework is suitable for dynamic environments where the desired system performance and resource usage changes dynamically while being constrained by limited amount of resources.
KEYWORDS: Sensors, Sensor networks, Control systems, Data storage, Data processing, Reliability, Environmental sensing, Detection and tracking algorithms, Pattern recognition, Data communications
We discuss a novel control methodology for power management in heterogeneous distributed sensor networks. Many algorithms for resource management in sensor networks require a comprehensive model of the external environment and the sensor network system, and are rule-based; this restricts their use in dynamic environments. We present an event-based control optimization formulation of the resource management problem and discuss a method to adaptively change desired system performance of the sensor network in response to events. This functionality is critical in field-deployable sensor networks where the available energy is extremely limited. This limitation disallows continuous operation as a very expensive option and necessitates system adaptation as a means to extend operational lifetime in the face of dynamic external events. We show results on synthetic sensor networks where only partially accurate information about the external world and the sensing system is available and illustrate the efficacy of the control algorithm in handling dynamic events with guaranteed minimum system lifespan via efficient usage of energy resources. We show that the control algorithm makes effective control decisions about the use of energy and storage resources with varying sensor reliabilities.
Eyetracking is one of the latest technologies that has shown potential in several areas including human-computer interaction for people with and without disabilities, and for noninvasive monitoring, detection, and even diagnosis of physiological and neurological problems in individuals. Current non-invasive eyetracking methods achieve a 30 Hz rate with possibly low accuracy in gaze estimation, that is insufficient for many applications. We propose a new non-invasive visual eyetracking system that is capable of operating at speeds as high as 6-12 KHz. A new CCD video camera and hardware architecture is used, and a novel fast image processing algorithm leverages specific features of the input CCD camera to yield a real-time eyetracking system. A field programmable gate array (FPGA) is used to control the CCD camera and execute the image processing operations. Initial results show the excellent performance of our system under severe head motion and low contrast conditions.
KEYWORDS: Cameras, Field programmable gate arrays, Signal processing, Imaging systems, Charge-coupled devices, CCD cameras, Logic, Image processing, Control systems, Process control
Commercially available cameras are not designed for the combination of single frame and high-speed streaming digital video with real-time control of size and location of multiple regions-of-interest (ROI). A new control paradigm is defined to achieve low-level camera control with high-level system operation. This functionality is achieved by defining the indivisible pixel read out operation on a per ROI basis with in-camera time keeping capability. This methodology provides a Random Access, Real-time, Event-driven (RARE) camera for adaptive camera control and is well suited for target tracking applications requiring autonomous control of multiple ROIs. This methodology additionally provides for reduced ROI read out time and higher frame rates compared to a predecessor architecture by avoiding external control intervention during the ROI read out process.
A robust acquisition, tracking and pointing (ATP) subsystem is being developed for the 2.5 Gigabit per second (Gbps) Unmanned-Aerial-Vehicle (UAV) to ground free-space optical communications link project. The demonstration will gather HDTV images of regions of geological interest (e.g. volcanic) and then downlink those images to ground receivers at a range of 50 km while the UAV is at an altitude of 18 km. With a 200 mW downlink laser at 1550 nm for a BER of 1E-9, the pointing requirements on the flight terminal are a jitter error of 19.5 urad and a bias error of 14.5 urad with a probability of pointing induced fades of 0.1 %. In order to mitigate the effect of atmospheric fades and deal with UAV flight and vibration uncertainties (relatively new craft) the ATP subsystem requirements have been set to a stringent level in order to assure success of the communication link. The design, analysis and development of this robust ATP subsystem will be described in this paper. The key innovations that have been developed to make the ATP subsystem robust are i) the application of inertial sensors to make the acquisition and tracking functions tolerant to atmospheric fades, ii) the usage of active exposure control to provide a 16 dB dynamic range on the Focal Plane Array (FPA) tracking window, and iii) the introduction of a second ultra wide field of view camera to assure acquisition of the ground beacon.
The functional requirements and design drivers for an Optical Communications subsystem are assessed based on the system requirements imposed by a proposed Europa Orbiter mission. Unlike near-Earth optical communications systems, deep space missions impose a unique set of requirements that drives the subsystem design. Significant challenges on laser efficiency, thermal control, pointing and tracking, stray/scatter light control, and subsystem mass/power need to be addressed for a successful subsystem implementation. The baseline design concept for a lasercom subsystem for the Europa orbiter mission employs a 30-cm diameter, diffraction-limited telescope, and a diode pumped solid state laser operating at 1.06 micrometer to support downlink communications. The baseline pointing and tracking approach is to perform Earth Image Tracking with occasional calibration using the Earth- moon or Earth-star images. At high phase angles when the Earth image does not provide sufficient brightness for high rate tracking, inertial sensors (accelerometers) measurements are used to propagate the knowledge of the optical boresight at a higher rate in between celestial reference updates. Additionally, uplink beacon tracking will be used to support pointing at short range and near solar opposition when Earth image alone does not provide sufficient signal power for tracking.
The Optical Communications Demonstrator (OCD) is a laboratory based lasercom terminal that was developed to validate several key technologies such as precision beam pointing, high bandwidth beacon tracking and beacon acquisition. The unique architecture of OCD uses a single focal plane array (FPA) and a single fine steering mirror (FSM) for beacon acquisition, beacon tracking and point-ahead compensation. A fiber-coupled laser transmitter further reduces the complexity of the terminal. Over the last year, system level integration, test and characterization of the terminal were conducted. Here we present results from the integration and test (I&T) of the terminal with the Lasercom Terminal Evaluation Station (LTES), with particular emphasis on the fine tracking performance. Furthermore, we will describe lessons learnt from the implementation and testing of OCD that are relevant to the design of future flight optical communication terminals. The completed OCD is now being used in a series of ground-ground experiments to understand atmospheric effects and to gain experience operating the OCD.
The Optical Communications Demonstrator (OCD), under development at the Jet Propulsion Laboratory (JPL), is a laboratory-based lasercomm terminal designed to validate several key technologies, primarily precision beam pointing, high bandwidth tracking, and beacon acquisition. The novelty of the instrument is that it uses a single CCD array detector for both beacon acquisition and tracking, and a fiber-coupled laser transmitter. The resulting reduction in design complexity can lead to a reduced system cost and an improved system reliability. In this paper, we describe recent progress on the development of the OCD terminal, particularly the electronics packaging and optical characterization with the Lasercom Test and Evaluation Station (LTES).
This paper describes several high performance computing testbeds being developed for Ballistic Missile Defense Organization applications that are based on high speed wavelength division multiplexed (WDM) fiber optic packet network technology. By combining high speed (> 100 Gb/s per channel), low latency (< 1 us), and scalability, these WDM networks offer the possibility of creating very closely coupled meta-supercomputers for real-time theater defense applications. The testbeds consist of: (1) coarse grain architecture consisting of a few large massively parallel processor supercomputers connected by striped WDM trunks, (2) fine grain architecture consisting of clusters of workstations connected by a fast WDM packet network, and (3) a hybrid satellite/WDM fiber network for global grid. These all-optic networks are expected to enable a number of distributed teraflop applications, such as real- time image fusion, real-time radar signature analysis and modeling, very large scale simulation, and realistic synthetic scene generation. This paper describes these testbeds in more detail and their specific WDM component requirements.
Nicholas Bambos, Joseph Bannister, Larry Bergman, Jason Cong, Eli Gafni, Mario Gerla, Leonard Kleinrock, Steve Monacos, Po-Chi Hu, B. Kannan, Bruce Kwan, Prasath Palnati, John Peck, Simon Walton
The Supercomputer Supernet (SSN) is a high-performance, scalable optical interconnection network for supercomputers and workstation cluster based on asynchronous, wormhole- routing switches. The WDM optical backbone extends the geographic coverage range from interdepartmental to campus and even to metropolitan areas with dynamically reconfigurable direct or multi-hop connections. The network provides very high-speed integrated services, supporting connection oriented, guaranteed bandwidth traffic as well as datagram traffic. The first networking level of the two-level SSN architecture is electronic and consists of crossbar meshes locally interconnecting work-stations, supercomputers, peripheral devices and mass memory. At a higher networking level, an optical backbone network supporting multiple wavelength division multiplexed (WDM) channels allows communication between devices connected to distinct crossbar meshes. In this paper, we focus on the protocols of the WDM optical backbone network and address the issue of integration of the electronic wormhole- routing LAN with the optical backbone.
Optical fiber networks may one day offer potential capacities exceeding 10 terabits/sec. This paper describes present gigabit network techniques for distributed computing as illustrated by the CASA gigabit testbed, and then explores future all-optic network architectures that offers increased capacity, more optimized level of service for a given application, high fault tolerance, and dynamic reconfigurability.
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