In this paper we describe a prototype surveillance system that leverages smart sensor motes, intelligent video, and
Sensor Web technologies to aid in large area monitoring operations and to enhance the security of borders and
critical infrastructures. Intelligent video has emerged as a promising tool amid growing concern about border
security and vulnerable entry points. However, numerous barriers exist that limit the effectiveness of surveillance
video in large area protection; such as the number of cameras needed to provide coverage, large volumes of data to
be processed and disseminated, lack of smart sensors to detect potential threats and limited bandwidth to capture and
distribute video data. We present a concept prototype that addresses these obstacles by employing a Smart Video
Node in a Sensor Web framework. Smart Video Node (SVN) is an IP video camera with automated event detection
capability. SVNs are cued by inexpensive sensor motes to detect the existence of humans or vehicles. Based on
sensor motes' observations cameras are slewed in to observe the activity and automated video analysis detects
potential threats to be disseminated as "alerts". Sensor Web framework enables quick and efficient identification of
available sensors, collects data from disparate sensors, automatically tasks various sensors based on observations or
events received from other sensors, and receives and disseminates alerts from multiple sensors. The prototype
system is implemented by leveraging intuVision's intelligent video, Northrop Grumman's sensor motes and
SensorWeb technologies. Implementation of a deployable system with Smart Video Nodes and sensor motes within
the SensorWeb platform is currently underway. The final product will have many applications in commercial,
government and military systems.
After a 5-year mission, the Near-Earth Asteroid Rendezvous-Shoemaker (NEAR) spacecraft made a controlled landing 12 February 2001 onto the asteroid, 433 Eros. Onboard the spacecraft, the NEAR Laser Rangefinder (NLR), a laser altimeter, gathered over 11 million measurements throughout 2000 and 2001, providing a spatially dense, high-resolution, topographical map of Eros. This instrument, launched in February 1996, was subjected to a constant, albeit, low radiation background predicted during the mission design phase to be 3 krad, cumulative, from solar protons at a shield depth of 1.8 mm aluminum. Using the onboard NLR calibration capability, and through extended observation of NLR measurement performance, the instrument exceeded requirements for this particular radiation environment. Electronic parts for the altimeter had been reviewed, assessed and screened, as necessary, for space quality and radiation hardness during its development. The NEAR mission included an excursion beyond Mars' orbit during its 4-year transit, followed by a one-year mission orbiting the near-Earth asteroid, 433 Eros, continuously collecting altimetry data. The majority of the data collection occurred during solar maximum and, in particular, operated without interruption through the events on Bastille Day, 14 July 2000 (comparable to the large October 1989 events of the previous solar maximum) and 10 November 2000. At Earth, the July 2000 proton level provided in a few days over half of the expected cumulative radiation, predicted through use of Feynman's model. Based on uneventful operation of the NEAR, including the absence of any degradation in solar array currents due to proton displacement damage and the nominal performance of the altimeter, it appears that the 14 July event did not intersect the NEAR location. The NLR-derived topographic data successfully enabled determination of Eros' shape, mass, and density contributing to the understanding the internal structure and collisional evolution of Eros.
After a 5-year mission, a 4-year transit followed by a one-year mission orbiting the asteroid 433 Eros, the Near-Earth Asteroid Rendezvous-Shoemaker (NEAR) spacecraft made a controlled landing onto the asteroid's surface on 12 February 2001. Onboard the spacecraft, the NEAR Laser Rangefinder (NLR) facility instrument had gathered over 11 million measurements, providing a spatially dense, high-resolution, topographical map of Eros. This topographic data, combined with Doppler tracking data for the spacecraft, enabled the determination of the asteroid's shape, mass, and density thereby contributing to understanding the internal structure and collisional evolution of Eros. NLR data indicate that Eros is a consolidated body with a complex shape dominated by collisions. The offset between the asteroid's center of mass and center of figure indicates a small deviation from a homogeneous internal structure that is most simply explained by variations in mechanical structure. Regional-scale relief and slope distributions show evidence for control of some topography by a competent substrate. It was found that pulse dilation was the major source of uncertainty in single-shot range measurements from the NLR, and that this uncertainty remains consistent with the overall 6-m range measurement system accuracy for NEAR. Analysis of NLR data fully quantified the geodynamic nature of this planetesimal, ergo, illustrating the utility of laser altimetry for remote sensing.
On February 14, 2000, after a 4-year transit, the recently renamed Near-Earth Asteroid Rendezvous (NEAR) Shoemaker spacecraft entered a 300-km orbit around the asteroid 433 Eros. Onboard the spacecraft, the NEAR Laser Rangefinder facility instrument began operation providing high-resolution topographical profiles of Eros. Developed at the Johns Hopkins University Applied Physics Laboratory, the NLR is a bistatic, direct-detection laser altimeter. The transmitter uses a gallium arsenide diode-pumped Cr:Nd:YAG laser at 1.064 micrometer. This lithium-niobate Q-switched transmitter emits 15-ns pulses at 15.3 mJ/pulse (1/8 to 8 Hz), permitting reliable NLR operation at the required 50-km altitude. The separate receiver employs an extended infrared-sensitive avalanche-photodiode detector with a 7.62-cm clear aperture Dall-Kirkham collecting telescope. End-to-end calibration capability exists between the transmitter and receiver via a 109.5-m spooled fiber-optic. A fraction of each emitted outgoing laser pulse is sampled, optically delayed and injected into the receiver optics providing a 'fixed target' to the NLR. In preparation for sampling Eros, the NLR has been operated numerous times during the 4-year transit period. These 'post-launch tests' provided housekeeping and calibration data useful in characterization and verification of the NLR design. This article summarizes the design used, post-launch test results, and implementation details used to control the NLR illustrating the complexity of operating an instrument in deep space. Additionally, preliminary evaluation of NLR performance using preliminary altimetry data of 433 Eros is presented.
Space-based laser altimeters are effective in providing topographic measurements critically important to the understanding of the formation and early evolution of planetary bodies. Using laser altimetry data, topographic grids can be produced that provide significant insight into the shape, internal structure and evolution of the subject body. Prime examples of space-based altimetry efforts are the Clementine and the Near-Earth Asteroid Rendezvous (NEAR) missions. Clementine spent two months sampling the Moon, and through its altimetry data, provided a glimpse of the lunar surface previously unseen. NEAR will place a laser altimeter (NLR) in orbit at the near-Earth asteroid 433 Eros for a one year observation period. Specifications for such altimeters are driven by mission requirements and host spacecraft constraints. Mission requirements usually prioritize observation objectives associated with other payload instruments, therefore, altimeter design must readily accommodate other payload instruments. Constraints placed on altimeters include mass, power, and volume; also for deep-space missions, data rates are limited and become an issue especially when imaging instruments are part of the mission. Altimeter performance specification and modeling to meet these requirements are described and approaches to verify instrument performance during pre-launch testing are provided. Lessons provided from laser altimetry missions indicate the technological progression to the next-generation laser altimeters.
The near earth asteroid rendezvous (NEAR) laser rangefinder (NLR), an instrument on the NEAR spacecraft, was designed to measure range from the NEAR spacecraft to the surface of the asteroid 433 EROS. The instrument consists of a laser transmitter, a calibration fiber, an optical receiver, analog electronics, power converting and conditioning electronics, and a digital processing unit. The digital processing unit controls configuration and operation of the transmitter and analog electronics. Software running in the processor handles communication between the spacecraft data bus and the NLR. The software includes functions for command handling, telemetry data formatting and data transfer to the command and data handling computer, transmitter control, measurement of the receiver noise floor, and correction of some timing delays. A brief overview of the software is given along with descriptions of auto-calibration sequences and test results.
The NEAR spacecraft was launched on February 17, 1996. Qualification tests conducted on the NEAR laser rangefinder allowed evaluation of the instrument's performance and provided calibration data prior to launch. From these data, we were able to determine the system electronic delays, the receiver rangewalk, and the receiver noise floor. The first operational test occurred on April 25, 1996. This post- launch test of the rangefinder verified survival of the instrument and provided data on the calibration parameters listed above. This paper describes these parameters and their significance to rangefinder operations. An interference test was conducted on May 22, 1996. This test allowed engineers to evaluate the effect of laser operations on data from other instruments. The post-launch test and interference are described and the results from these test are presented.
A direct-detection laser altimeter is one of five instruments supporting the one-year scientific investigation of the near-Earth asteroid, 433 Eros, the subject of the near-earth asteroid rendezvous (NEAR) mission. While orbiting Eros at an altitude of 50 km, the NEAR laser rangefinder will continuously sample Eros' surface. Evaluation of altimeter performance requires an understanding of pertinent asteroid characteristics, mission geometry, and rangefinder implementation of the Neyman- Pearson detection criterion. Analysis indicates performance margin of 9.8 dB at 50 km in the presence of speckle. The altimeter is a bistatic configuration that uses a 15 mJ/pulse Cr:Nd:YAG solid-state laser and 3.5-inch aperture Dall-Kirkham receiver telescope with low-noise, high-speed detection electronics. This paper presents pertinent mission requirements and highlights the altimeter design. Our analysis is described and results from altimeter testing are provided demonstrating 9 - 12 dB performance margin, in agreement with prediction.
The near earth asteroid rendezvous (NEAR) laser rangefinder (NLR) is a bistatic system using a diode-pumped Nd:YAG laser and a Dall-Kirkhamm telescope for a receiver. The NLR is one of a suite of five scientific data gathering instruments on the NEAR spacecraft. The NEAR mission is the first of NASA's Discovery Series of spacecraft. The NLR transmitter emits a 15.6 mJ, 15 ns pulse at 1064 nm. The receiver is capable of reliably detecting return signals from the asteroid as low as 1 fJ per pulse, which corresponds to an average power of 50 nW (20 ns pulse). The development and alignment approach of the bistatic system are discussed. The performance test results of the receiver, transmitter, and integrated rangefinder system are presented. Particular attention is given to the system alignment tests and an open air range verification test.
The NEAR laser range finder (NLR) design is a compact, light weight design with a high power laser transmitter and a high performance mirror receiver system. One of the main objectives of the NLR is to provide the in-situ distance measurement from the spacecraft to a near earth asteroid. An on board computer will compile this information to provide necessary navigation requirements for the NEAR satellite. Due to the weight budget constraint, the maximum weight limitation of the NLR has been a critical issue from the beginning of the program. To achieve this goal and meet the system design objectives, innovative designs have been implemented in the development of light weight optical, mechanism, and electronic packaging hardware. This paper provides details of the NLR electronic packaging design, thermal and structural designs.
The qualification of the NEAR laser transmitter is discussed with emphasis placed on the three major problem areas encountered: (1) use and derating of discrete power supply components; (2) application of a non-hermetic, high voltage hybrid to the space environment; and (3) vibration testing of the laser optics train. Summary comments are made with respect to the predictability of these quality/reliability problems.
In 1999 after a 3-year transit, the Near-Earth Asteroid Rendezvous (NEAR) spacecraft will enter a low-altitude (approximately 50 km) orbit about the asteroid, 433 Eros. Five instruments, including a laser radar, will operate continuously during the one-year orbit at Eros. The NEAR laser rangefinder (NLR), developed at the Applied Physics Laboratory (APL), is a robust rangefinder and the first spaceborne altimeter to have continuous inflight calibration capability. A bistatic configuration, the NLR uses a diode- pumped Cr:Nd:YAG transmitter and a leading-edge receiver with a 3.5-inch aperture Dall-Kirkham telescope. Detection is accomplished using an enhanced-silicon avalanche photodiode. From system tests, the NLR is capable of ranging in excess of 100 km to the asteroid's surface. Measurements of the time-of-flight between laser pulse firings and detection of surface backscatter are made using an APL- developed receiver having range resolution of 31.48 cm and accuracy of 2 m. Total mass of the NLR is 4.9 kg and its average power consumption is <EQ 15.1 W. This paper reviews specifications for the NLR instrument, provides overall design details, and presents system performance using prelaunch test results.
The Near Earth Asteroid Rendezvous (NEAR) mission is the first mission of the NASA Discovery Program. The NEAR spacecraft, developed and tested by the Johns Hopkins University Applied Physics Laboratory (JHU/APL), embarked on a four year mission on February 17, 1996. During the three- year cruise phase, the satellite will fly near the asteroid Mathilde and will receive an energy boost during an Earth swing-by in 1998. In 1999 NEAR will begin its year long orbit around the asteroid 433 Eros to collect scientific data using several instruments including an imager, a magnetometer, an X-ray/Gamma-ray detector, and a laser altimeter. The NEAR Laser Rangefinder (NLR) will provide altimetry data for characterizing the topography of Eros from a distance of 42 km. The instrument was designed and tested to meet the requirements of the NEAR space environment. In this paper we review the NLR design, present the test philosophy, highlight the tests, and present test results.
The Near Earth Asteroid Rendezvous (NEAR) Laser Rangefinder (NLR) is a bistatic system using a diode pumped Nd:YAG laser and a Dall-Kirkham telescope for a receiver. The NLR is one of a suite of five scientific data gathering instruments on the NEAR spacecraft. The NLR receiver is sensitive to incident IR radiation (1064 nm) and can detect return signals from the asteroid as low as 0.1 fJ per pulse, which corresponds to an average power of 9 nW (10 ns pulse). The design, development,a nd testing of the receiver will be discussed in this paper. Technological legacies from other space based programs were significant in meeting the schedule and cost requirements of a Discovery series program and will be discussed herein. Finally, the development of a cost effective, low impact, Level 50 clean area (pivotal in achieving the required environment for integration and test) will be presented.
The near-earth asteroid rendezvous (NEAR) mission is the first of the NASA discovery programs. Discovery-class programs emphasize small, low-cost, quick turnaround space missions that provide significant science returns. The NEAR spacecraft and ground control system are currently being developed and tested at the Applied Physics Laboratory (APL). The NEAR spacecraft will orbit, 433 Eros, possibly the most studied of the near-Earth asteroids. Subsequent to a 3-year cruise, the NEAR spacecraft is inserted into a 50-km-altitude orbit about Eros for 1 year to permit data collection in the infrared, visible, x-ray and gamma-ray regions. One instrument, the NEAR laser rangefinder (NLR), will provide altimetry data useful in characterizing the geophysical nature of Eros. In addition, ranging data from the NLR will support navigation functions associated with spacecraft station-keeping and orbit maintenance. The NLR instrument uniquely applies several technologies for use in space. Our configuration uses a direct-detection, bistatic design employing a gallium arsenide (GaAs) diode-pumped Cr:Nd:YAG laser for the 1.064-micrometer transmitter and an enhanced-silicon avalanche-photodiode (APD) detector for the receiver. Transmitter pulse energy provides the required signal-to-noise power ratio, SNRp, for reliable operation at 50 km. The selected APD exhibited low noise, setting the level achievable for noise equivalent power, NEP, by the receiver. The lithium-niobate (LiNbO3) Q-switched transmitter emits 12-ns pulses at 15.3 mJ/pulse, permitting reliable NLR operation beyond the required 50-km altitude. Cavity aperturing and a 9.3X Galilean telescope reduce beam divergence for high spatial sampling of Eros's surface. Our receiver design is an f/3.4 Dall-Kirkham Cassegrain with a 7.62-cm clear aperture -- we emphasized receiver aperture area, Arx, over transmitter power, Pt, in our design based on the range advantage attainable according to the simplified range equation, Rmax equals [(Pt(rho) BArx)/(SNRp NEP)]1/2. Asteroid reflectivity, (rho) B, is estimated to be 0.05 at our wavelength. A reasonable power signal- to-noise ratio for reliable operation, SNRp, was assumed. To minimize our noise equivalent power, NEP, we carefully designed and selected the receiver components. The receiver circuit uses leading-edge detection of the laser backscatter. Our detector circuit is an enhanced-silicon APD hybrid using a video amplifier, an integrating Bessel filter, and a high- speed programmable threshold comparator. We accomplish time-of-flight (TOF) measurements digitally with an APL-designed GaAs application-specific integrated circuit. A radiation-hardened FORTH microprocessor controls range gating, data collection and formatting, and operational modes. Implementation of control and data communications between the spacecraft and rangefinder uses the MIL-STD 1553-bus architecture. Functional testing and calibration indicate exceptional performance; return power levels were reliably detected over several thresholds with 71-dB attenuation, while observed range jitter was equivalent to the resolution determined by the TOF GaAs chip (31.5 cm). This paper discusses NLR performance requirements, design implementation, and qualification testing. It also provides preliminary results from calibration and performance testing.
A time-frequency distribution (TFD) signal processor, developed at the Applied Physics Laboratory, is currently under evaluation using simulated signals and actual laser vibration sensor (LVS) data that we collected on various ship targets. Preliminary results for one instantaneous frequency (IF) estimator implementation, the smoothed cross Wigner-Ville Distribution (XWVD), indicate 8 to 10 dB demodulation (CNR) advantage compared to a digital FM limiter-discriminator. A second approach, using the unsmoothed XWVD TFD, demonstrated a 3-5 dB advantage. Regarding spectral estimation, we are investigating performance of our reduced interference distribution (RID) implementation through comparison with the short-time Fourier transform (STFT). From the LVS data processed, indications are that a significant increase in spectral and temporal resolution exists using our RID approach. Our processor also provided improved detectability over the STFT for transient signals and short-lived sinusoids. Significant correlation between accepted acoustic lines and LVS-derived vibration lines are indicated. Details are presented that describe our signal simulation, the LVS measurements, and signal processing implementations along with assumptions based on measured speckle-induced amplitude modulation.
This course addresses the use of ad hoc network sensors to implement "smart" reconnaissance with various objectives: vehicular/personnel detection and tracking, persistent surveillance, perimeter control, and/or continuous event monitoring (including Military Operation in Urban Terrain, MOUT). The course presents the use of small (<30 in3) micro-sensors (referred to as "motes") within a wireless ad hoc network. The object is to perform tasks previously assigned to larger, more power hungry, sophisticated sensors such as imaging, acoustic, and/or seismic sensors. Through distributed processing of sensor signals within a networked field, motes can accomplish a myriad of tasks formerly relegated to larger sensors. Additionally, mote "fields" can be applied using numerous configurations that allow for novel security and/or military applications.
This course introduces the technologies and markets that spawned mote-sized wireless sensors, discusses the design of motes and associated sensors, reveals the mote middleware functionality and implementation requirements, and provides insight concerning mote-field C2 interfaces. Examples are provided, with background information that presents low power ad hoc networking, mote-based sensor design rules, middleware implementations, and issues associated with data exfiltration and mote field deployment.
Actual implementations of mote arrays in laboratory and field environments are reviewed along with underlying mote designs for specific applications. Efforts in self-organizing wireless networks stem from several sources: notably DARPA's Network Embedded Sensor Technology program http://www.darpa.mil/ipto/programs/nest/nest.asp (NEST) will be discussed.