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The maximum obtainable resolution of a strip-map synthetic aperture radar (SAR) system can be retained by simply avoiding weighting, or tapering, data samples in the along-track compression process. However, this will lead to hazardous artifacts caused by strong sidelobes of the corresponding adjacent scatterers whose interference might severely weaken the desired targets or even introduce false targets...
Remote sensing of terrestial and planetary surfaces in the infrared for the purpose of identifying minerals and their distribution is an ongoing activity. The huge amount of spectral data currently available and expected from future space missions presents a challenge to the scientist determine to extract useful scientific information from this data. Automated methods to facilitate this process are...
For cognitive radio technology, energy detection using the fast Fourier transform (FFT) is a common technique for spectrum sensing so that underutilized frequency bands can be opportunistically used while causing no detrimental interference to the primary user. However, traditional detection and false alarm rate analyses of FFT-based detectors require incorporating the characteristics of the propagation...
In this paper, we propose a fast and reliable data dissemination protocol Cascades to disseminate data from the sink(base station) to all or a subset of nodes in a data collection sensor network. Cascades makes use of the parent-monitor-children analogy to ensure reliable dissemination. Each node monitors whether or not its children have received the broadcast messages through snooping children's...
Modeling an integrated global positioning system / inertial navigation system (GPS/INS) in an optimal sense involves taking into account the non-linear relationships that exist in the physical real world model. Utilizing non-linear filtering techniques such as particle filters instead of the sub optimal Kalman filter and its variants allows one to more accurately model systems of this nature. Systems...
Uplink array technology is currently being developed for NASA's Deep Space Network (DSN) to provide greater range and data throughput for future NASA missions, including manned missions to Mars and exploratory missions to the outer planets, the Kuiper belt, and beyond. Here we describe a novel technique for generating the frequency predicts that are used to compensate for relative Doppler, derived...
This paper reports on a study of hybrid optical/radio frequency (RF) architectures for deep space missions. Previous proposed optical deep space communication architectures were generally designed to achieve 90% or better availability 24/7. This study, instead, considered alternative metrics and architectures. It focuses on a strategy to use RF links and existing RF infrastructure for navigation and...
Since 2004, afterwards the US announcement, a renewed spirit of exploration has pushed space agencies in the world to promote new programs and studies devoted both to return to the Moon and to prepare a human mission toward Mars. Main objectives of this new phase of the space exploration is to collect as many as possible science data of the two planetary bodies and to acquire and test the technological...
Orbit at the critical inclination is a practical option for long-term satellite formations flying around an oblate Earth. This paper establishes that passive and periodic relative orbits with cross-track motion are only possible at the critical inclination under conditions that all satellites share the same inclination, the same semi-major axis and the same eccentricity. Furthermore, a quasi-periodic...
Since the 70s Italy has had a pioneering approach to higher frequencies, at first at Ka band (20/30 GHz) with the Sirio experience (launched in 1978), when such a range was still a frontier, and then with Italsat F1 and F2 experiments in the 90s, studying Q and V bands in addition to Ka one as well. After those experiences, Italy through the Italian space agency (ASI) was one of the first European...
Formation design considering the eccentricity and the J2 perturbation is significant for a practical satellite formation flying mission. The linear solution of satellite relative motion proves that, by setting all satellites having the same mean orbit elements of semi-major axis, eccentricity, inclination and right ascension of ascending node, a passive in-plane formation is periodic and stable in...
In this paper requirements, specifications and preliminary system design of a mini-satellite flower constellation for millimeter-wave atmospheric observations are presented together with the main payload technological characteristics. This work has been performed in the frame of FLORAD Phase A project (mini-satellite FLOwer constellation of millimeter-wave RADiometers for atmospheric observations),...
A basic requirement for a satellite's formation is the precise knowledge of the spacecraft's relative configuration. The design of the navigation subsystem is significantly affected by this peculiar issue: in fact, the accuracy required for the fulfillment of the formation tasks is much greater than the one usually required for a single satellite.
During the Apollo landings, onboard astronauts, along with analysis and instructions from mission control, performed the majority of complex tasks beyond automated guidance, navigation, and control (GN&C). The crew played a significant role in the landings and were critical to navigating to the landing site, selecting a safe landing aim point, and commanding the spacecraft via a hand controller...
Small spacecraft have been increasing in popularity because of their low cost, short turnaround and relative efficiency. In the past, small spacecraft have been primarily used for technology demonstrations, but advances in technology have made the miniaturization of space science possible. PharmaSat is a low cost, three cube size nanosatellite spacecraft, with a biological experiment on board, built...
In this paper, we present an experimental study of sun sensing as a rover navigational aid. Algorithms are outlined to determine (i) rover heading in an absolute reference frame and (ii) absolute rover position (i.e., latitude/longitude). Our sensor suite consists of a sun sensor, inclinometer, and clock (as well as ephemeris data). We describe a technique to determine ground-truth orientation in...
Active and passive approaches to accommodating moderate rover slip during coring, using a body mounted coring tool were studied. The work addresses the possibility of a 200 kg rover experiencing moderate slip such as 1 cm/minute while coring on a Martian slope using a body-mounted coring tool in a possible future Mars Sample Return mission. Rover slip while coring could be accommodated with passive...
A percussive digging system has been demonstrated to decrease the amount of downforce needed to penetrate a given soil, thus reducing the required reaction loads and robot mass. Preliminary testing of a percussive digging system in compacted lunar regolith simulant, JSC-1A, has demonstrated a 15 x (fifteen times) reduction in the downforce necessary to penetrate the regolith. Downforce reductions...
To ensure that robots are used effectively for exploration missions, it is important to assess their performance during operations. We are investigating the definition and computation of performance metrics for assessing remote robotic operations in real-time. Our approach is to monitor data streams from robots, compute performance metrics, and provide Web-based displays of these metrics for assessing...
Through the National Security Space Acquisition Policy (NSSAP) 03-01 the United States Air Force requires an Independent Program Assessment (IPA) prior to each Key Decision Point (KDP) program milestone decision by the Defense Space Acquisition Board (DSAB). The goal of an IPA is to ensure a program is ready to pass into the next milestone. During the IPA process the acquisition experts on the IPA...
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