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This document is a compilation of the workshop agenda and presentation materials from the Alabama CSS Workshop in Tuscaloosa, Alabama.
We report detailed follow-up observations of eight cataclysmic variable stars (CVs) that are apparently AM Her stars, also called polars. For all, we either determine orbital periods for the first time or improve on existing determinations. The seven for which we have spectra show the high-amplitude radial-velocity curves and prominent He ii λ4686 emission lines characteristic of strongly magnetic CVs, and their periods, which range from 81 to 219 minutes, are also typical for AM Her stars. Two objects from the Gaia-alerts index, Gaia18aot and Gaia18aya, are newly identified as CVs. Another, RX J0636.3+6554, eclipses deeply, while CSS 080228:081210+040352 shows a sharp dip that is apparently a partial eclipse. The spectrum of Gaia18aya has a cyclotron harmonic near λ5500 Å that constrains the surface field to ∼49 MG or greater.
High-precision light curves were extracted from TESScut images. Together with APOGEE and LAMOST medium-resolution spectra, a joint study was made for six early K-type contact binary candidates selected unbiasedly with orbital periods around 0.268 day. It is found that all of them (RV CVn, EK Com, V384 Ser, V1038 Her, EH CVn, and CSS_J125403.7+503945) are W-subtype shallow contact systems, though with different mass ratios (1/q = 0.27–0.62). The effective temperature differences between the binary components are around a few hundred kelvins. The original definitions of the A and W subtypes were compared with the customarily used methods, which rely on the shape or photometric solutions of the light curves. The latter two methods are not always reliable; therefore, the radial velocity analysis is strongly recommended. Through a collection of all available K-type contact binaries with both photometric and spectroscopic measurements, it is found that almost all of them are W-subtype systems, except for a few objects that have nearly identical temperatures for binary components. This W-subtype phenomenon for K-type contact binaries should be further checked with more samples in the future. Finally, the physical parameters of the targets were determined with joint data analysis, and the multiplicity is discussed for these targets. Objects V384 Ser and RV CVn are confirmed to very likely be triple systems from comprehensive analysis, while V1038 Her is a candidate of a triple system based on photometric and spectroscopic solutions.
A boundary collocation method has been employed to determine the Mode II stress intensity factors for a pair of through-the-thickness edge cracks in a finite isotropic plate. An elastostatic analysis has been carried out in terms of the complete Williams stress function employing both even and odd components. The results of the numerical analysis were verified by a two-step procedure whereby the symmetric and antisymmetric portions of the solution were independently compared with existing solutions. The complete solution was verified by comparison with a photoelastic analysis. A compact shear specimen (CSS) of Hysol epoxy resin was loaded in a photoelastic experiment designed to study the isochromatic fringe patterns resulting from the Mode II crack tip stress distribution. The experiment verified that a pure Mode II stress distribution existed in the neighborhood of the crack tips and confirmed the accuracy of the boundary collocation solution for the Mode II stress intensity factors.
A preliminary analysis of the data obtained during entry of the STS-4 Flight was completed. Planned maneuvers were flown during this flight to increase the quality of stability and control analysis, similar to the techniques used during STS-3. The derivatives obtained from STS-4 agreed fairly well with the derivatives obtained on previous flights. The dependence of aileron effectiveness on a elevon position above a Mach number of 10 seen on STS-3 was conclusively verified on STS-4. CSS Mode was engaged to fly the heading alignment circle. After engagement, several cycles of a low amplitude pilot induced oscillation (1 deg/sec) at about 0.3 hertz can be seen. No PIO suppressor activity was seen between preflare and touchdown. This approach demonstrates the advantage of the shallow final glideslope approach. In this type of approach, the pilot is not required to make accurate altitude judgments since an acceptable landing can be made without performing the final flare.
The Columbia has completed a spectacularly successful four flight Orbital Flight Test program as well as the first operational mission in which two satellites were deployed. It is unprecedented that a vehicle so complex as the Shuttle could have reached such a state of maturity in so few missions. This maturity is reflected not only in terms of basic performance during dynamic flight phases, but also in the outstanding performance of individual spacecraft systems. Appreciably more CSS time has been logged during entry and particularly in the approach and landing phase than any other segment of the mission profile. The discussion that follows, therefore, will outline this phase in some detail including pilot comments, techniques, crew displays and landing aids. Some problem areas related to landing the Orbiter will be discussed, as well as possible solutions.
The University of Texas at Dallas (UTD) Center for Space Sciences (CSS) has designed, developed, and fabricated three miniature mass spectrometers and their associated instrumentation in fulfillment of a NASA contract. The ion mass spectrometer analyzers furnished under this contract were modeled after a unit developed during a previous NASA grant. Three assemblies are described: (1) the magnetic sector; (2) the ion detector; and (3) the amplifier and power supply.
The Upper Atmosphere Research Satellite (UARS) uses fixed-head star trackers (FHST's) and inertial reference units (IRU's) to determine and control its attitude. This combination of fine sensors results in attitude knowledge accuracies to better than 10 arc-seconds (1 sigma). UARS also has a variety of coarse attitude sensors on board: the three-axis magnetometer (TAM), the coarse Sun sensor (CSS), the fine Sun sensor (FSS), and the Earth sensor assembly (ESA). By comparing attitude solutions using coarse sensors with FHST-determined attitude solutions, estimates can be made of the accuracy of the coarse sensors. This paper presents the results of an analysis that compares attitude solutions using various combinations of UARS coarse attitude sensor data with FHST attitude solutions.
The generation and validation of operations procedures is a key task of mission preparation that is quite complex and costly. This has motivated the development of software applications providing support for procedures preparation. Several applications have been developed at MATRA MARCONI SPACE (MMS) over the last five years. They are presented in the first section of this paper. The main idea is that if procedures are represented in a formal language, they can be managed more easily with a computer tool and some automatic verifications can be performed. One difficulty is to define a formal language that is easy to use for operators and operations engineers. From the experience of the various procedures management tools developed in the last five years (including the POM, EOA, and CSS projects), MMS has derived OPSMAKER, a generic tool for procedure elaboration and validation. It has been applied to quite different types of missions, ranging from crew procedures (PREVISE system), ground control centers management procedures (PROCSU system), and - most relevant to the present paper - satellite operation procedures (PROCSAT developed for CNES, to support the preparation and verification of SPOT 4 operation procedures, and OPSAT for MMS telecom satellites operation procedures).
This paper presents an overview of the Tropical Rainfall Measuring Mission (TRMM) Attitude Control System (ACS) along with detailed in-flight performance results for each operational mode. The TRMM spacecraft is an Earth-pointed, zero momentum bias satellite launched on November 27, 1997 from Tanegashima Space Center, Japan. TRMM is a joint mission between NASA and the National Space Development Agency (NASDA) of Japan designed to monitor and study tropical rainfall and the associated release of energy. Launched to provide a validation for poorly known rainfall data sets generated by global climate models, TRMM has demonstrated its utility by reducing uncertainties in global rainfall measurements by a factor of two. The ACS is comprised of Attitude Control Electronics (ACE), an Earth Sensor Assembly (ESA), Digital Sun Sensors (DSS), Inertial Reference Units (IRU), Three Axis Magnetometers (TAM), Coarse Sun Sensors (CSS), Magnetic Torquer Bars (MTB), Reaction Wheel Assemblies (RWA), Engine Valve Drivers (EVD) and thrusters. While in Mission Mode, the ESA provides roll and pitch axis attitude error measurements and the DSS provide yaw updates twice per orbit. In addition, the TAM in combination with the IRU and DSS can be used to provide pointing in a contingency attitude determination mode which does not rely on the ESA. Although the ACS performance to date has been highly successful, lessons were learned during checkout and initial on-orbit operation. This paper describes the design, on-orbit checkout, performance and lessons learned for the TRMM ACS.
The Microwave Anisotropy Probe (MAP) was launched June 30, 2001 to create an all-sky map of the Cosmic Microwave Background. The mission's hardware suite included two Lockheed Martin AST-201 star trackers, two Kearfott Two-Axis Rate Assemblies (TARAs) mounted to provide X, Y and redundant Z-axis rates, two Adcole Digital Sun Sensor (DSS) heads sharing one set of electronics, twelve Adcole Coarse Sun Sensor (CSS) eyes, three Ithaco E-sized Reaction Wheel Assemblies (RWAs), and a Propulsion Subsystem that employed eight PRIMEX Rocket Engine Modules (REMs). This hardware has allowed MAP to meet its various Orbit and Attitude Control Requirements, including performing a complex zero-momentum scan, meeting its attitude determination requirements, and maintaining a trajectory that places MAP in a lissajous orbit around the second Sun-Earth Lagrange point (L2) via phasing loops and a lunar gravity assist. Details of MAP's attitude determination, attitude control, and trajectory design are presented separately. This paper will focus on the performance of the hardware components mentioned above, as well as the significant lessons learned through the use of these components. An emphasis will be placed on spacecraft design modifications that were needed to accommodate existing hardware designs into the MAP Observatory design.
The NASA combustion branch is a leader in developing and applying combustion science to focused aerospace propulsion systems concepts. It is widely recognized for unique facilities, analytical tools, and personnel. In order to better communicate the outstanding research being done in this Branch to the public and other research organization, a more substantial website was desired. The objective of this project was to build an up-to-date site that reflects current research in a usable and attractive manner. In order to accomplish this, information was requested from all researchers in the Combustion branch, on their professional skills and on the current projects. This information was used to fill in the Personnel and Research sections of the website. A digital camera was used to photograph all personnel and these photographs were included in the personnel section as well. The design of the site was implemented using the latest web standards: xhtml and external css stylesheets. This implementation conforms to the guidelines recommended by the w3c. It also helps to ensure that the web site is accessible by disabled users, and complies with Section 508 Federal legislation (which mandates that all Federal websites be accessible). Graphics for the new site were generated using the gimp (www.gimp.org) an open-source graphics program similar to Adobe Photoshop. Also, all graphics on the site were of a reasonable size (less than 20k, most less than 2k) so that the page would load quickly. Technologies such as Macromedia Flash and Javascript were avoided, as these only function on some clients which have the proper software installed or enabled. The website was tested on different platforms with many different browsers to ensure there were no compatibility issues. The website was tested on windows with MS IE 6, MSIE 5 , Netscape 7, Mozilla and Opera. On a Mac, the site was tested with MS IE 5 , Netscape 7 and Safari.
The National Aeronautics and Space Administration s (NASA) Lunar Reconnaissance Orbiter (LRO) launched on June 18, 2009 from the Cape Canaveral Air Force Station aboard an Atlas V launch vehicle and into a direct insertion trajectory to the oon. LRO, which was designed, built, and operated by the NASA Goddard Space Flight Center in Greenbelt, MD, is gathering crucial data on the lunar environment that will help astronauts prepare for long-duration lunar expeditions. The mission has a nominal life of 1 year as its seven instruments find safe landing sites, locate potential resources, characterize the radiation environment, and test new technology. To date, LRO has been operating well within the bounds of its requirements and has been collecting excellent science data images taken from the LRO Camera Narrow Angle Camera of the Apollo landing sites appeared on cable news networks. A significant amount of information on LRO s science instruments is provided at the LRO mission webpage. LRO s Guidance, Navigation and Control (GN&C) subsystem is made up of an onboard attitude control system (ACS) and a hardware suite of sensors and actuators. The LRO onboard ACS is a collection of algorithms based on high level and derived requirements, and reflect the science and operational events throughout the mission lifetime. The primary control mode is the Observing mode, which maintains the lunar pointing orientation and any offset pointing from this baseline. It is within this mode that all science instrument calibrations, slews and science data is collected. Because of a high accuracy requirement for knowledge and pointing, the Observing mode makes use of star tracker (ST) measurement data to determine an instantaneous attitude pointing. But even the star trackers alone do not meet the tight requirements, so a six-state Kalman Filter is employed to improve the noisy measurement data. The Observing mode obtains its rate information from an inertial reference unit (IRU) and in the event of an IRU failure, the rate data is be derived from the star tracker, but with degraded pointing performance. The Delta-V control mode responsibility is to maintain attitude pointing during the cruise trajectory, insertion burns and lunar orbit maintenance by adjustments made to the spacecraft s velocity magnitude and vector direction. The ACS also provides for a thruster based system momentum management algorithm (known as Delta-H) to maintain the system and wheel momentum to within acceptable levels. In the event an anomaly causes the LRO spacecraft to lose the ability to maintain its current attitude pointing, a Sun Safe mode is included in the ACS for the purpose of providing a known power and thermally safe coarse inertial sun attitude for an indefinite period of time, within the manageable limits of the reaction wheels. The Sun Safe mode is also the initial spacecraft control mode off of the launch vehicle and provides for a means to null tip-off rates immediately after separation. The nominal configuration is to use the IRU for rate information in the controller. In the event of a gyro failure a gyroless control mode was developed that computes rate information from the CSS data.
Over the past decade, the dedicated search for kilometer-size near-Earth objects (NEOs), potentially hazardous objects (PHOs), and potential Earth impactors has led to a boost in the rate of discoveries of these objects. The catalog of known NEOs is the fundamental ingredient used to develop a model for the NEOs population, either by assessing and correcting for the observational bias (Jedicke et al., 2002), or by evaluating the migration rates from the NEOs source regions (Bottke et al., 2002). The modeled NEOs population is a necessary tool used to track the progress in the search of large NEOs (Jedicke et al., 2003) and to try to predict the distribution of the ones still undiscovered, as well as to study the sky distribution of potential Earth impactors (Chesley & Spahr, 2004). We present a method to model the NEOs population in all six orbital elements, on a finely grained grid, allowing us the design and test of targeted and optimized search strategies. This method relies on the observational data routinely reported to the Minor Planet Center (MPC) by the Catalina Sky Survey (CSS) and by other active NEO surveys over the past decade, to determine on a nightly basis the efficiency in detecting moving objects as a function of observable quantities including apparent magnitude, rate of motion, airmass, and galactic latitude. The cumulative detection probability is then be computed for objects within a small range in orbital elements and absolute magnitude, and the comparison with the number of know NEOs within the same range allows us to model the population. When propagated to the present epoch and projected on the sky plane, this provides the distribution of the missing large NEOs, PHOs, and potential impactors.
The Content Documents are created and managed under the System Software group with. Launch Control System (LCS) project. The System Software product group is lead by NASA Engineering Control and Data Systems branch (NE~C3) at Kennedy Space Center. The team is working on creating Operating System Images (OSI) for different platforms (i.e. AIX, Linux, Solaris and Windows). Before the OSI can be created, the team must create a Content Document which provides the information of a workstation or server, with the list of all the software that is to be installed on it and also the set where the hardware belongs. This can be for example in the LDS, the ADS or the FR-l. The objective of this project is to create a User Interface Web application that can manage the information of the Content Documents, with all the correct validations and filters for administrator purposes. For this project we used one of the most excellent tools in agile development applications called Ruby on Rails. This tool helps pragmatic programmers develop Web applications with Rails framework and Ruby programming language. It is very amazing to see how a student can learn about OOP features with the Ruby language, manage the user interface with HTML and CSS, create associations and queries with gems, manage databases and run a server with MYSQL, run shell commands with command prompt and create Web frameworks with Rails. All of this in a real world project and in just fifteen weeks!
There were many links calculated for this and the other scenarios. The rain was analyzed for 99.9% availability with rain rated of none, 20 mm/hr and 90 mm/hr at a height of 5 km out to 25 NM. This was done for each scenario for LOS and for BLOS links for Scenario 5 and 6. Scenario 1 was a LOS-only scenario. Use of two 3 dB Antennas on both ends. The CS2 was unable to maintain a control RF Link during the flight. The largest access gap periods between object top and bottom UA antennae were caused by terrain (ridges and hills). The CS Antenna was changed to High Gain Directional Antenna, all three CS maintained lock on vehicle. There were RF dropouts between the top and bottom UA antennae caused by aircraft obstructions (fuselage, wings, wheel assembles, etc.). Note that for this study antenna locations were placed on top and bottom center of the UA body. Future study should include actual UA antenna locations on the aircraft providing manufactures are willing to provide information. The importance of CS location(s) was demonstrated for primary or backup CS. With a second backup CS placed in a suitable location the UA was able to maintain an overall RF link. The actual location of both backup CSs required the antenna location to be place 150 ft above ground in order to establish a RF link between the UA and CS.
Current and future aerospace requirements demand the creation of a new breed of sensing devices, with emphasis on reduced weight, power consumption, and physical size. This new generation of sensors must possess a high degree of intelligence to provide critical data efficiently and in real-time. Intelligence will include self-calibration, self-health assessment, and pre-processing of raw data at the sensor level. Most of these features are already incorporated in the Wireless Sensors Network (SensorNet(TradeMark)), developed by the Instrumentation Group at Kennedy Space Center (KSC). A system based on the SensorNet(TradeMark) architecture consists of data collection point(s) called Central Stations (CS) and intelligent sensors called Remote Stations (RS) where one or more CSs can be accommodated depending on the specific application. The CS's major function is to establish communications with the Remote Stations and to poll each RS for data and health information. The CS also collects, stores and distributes these data to the appropriate systems requiring the information. The system has the ability to perform point-to-point, multi-point and relay mode communications with an autonomous self-diagnosis of each communications link. Upon detection of a communication failure, the system automatically reconfigures to establish new communication paths. These communication paths are automatically and autonomously selected as the best paths by the system based on the existing operating environment. The data acquisition system currently under development at KSC consists of the SensorNet(TradeMark) wireless sensors as the remote stations and the central station called the Radio Frequency Health Node (RFHN). The RFF1N is the central station which remotely communicates with the SensorNet(TradeMark) sensors to control them and to receive data. The system's salient feature is the ability to provide deterministic sensor data with accurate time stamps for both time critical and non-time critical applications. Current wireless standards such as Zigbee(TradeMark) and Bluetooth(Registered TradeMark) do not have these capabilities and can not meet the needs that are provided by the SensorNet technology. Additionally, the system has the ability to automatically reconfigure the wireless communication link to a secondary frequency if interference is encountered and can autonomously search for a sensor that was perceived to be lost using the relay capabilities of the sensors and the secondary frequency. The RFHN and the SensorNet designs are based on modular architectures that allow for future increases in capability and the ability to expand or upgrade with relative ease. The RFHN and SensorNet sensors .can also perform data processing which forms a distributed processing architecture allowing the system to pass along information rather than just sending "raw data points" to the next higher level system. With a relatively small size, weight and power consumption, this system has the potential for both spacecraft and aircraft applications as well as ground applications that require time critical data.
The purpose of this project is to utilize Ruby on Rails to create a web application that will replace a spreadsheet keeping track of training courses and tasks. The goal is to create a fast and easy to use web application that will allow users to track progress on training courses. This application will allow users to update and keep track of all of the training required of them. The training courses will be organized by group and by user, making readability easier. This will also allow group leads and administrators to get a sense of how everyone is progressing in training. Currently, updating and finding information from this spreadsheet is a long and tedious task. By upgrading to a web application, finding and updating information will be easier than ever as well as adding new training courses and tasks. Accessing this data will be much easier in that users just have to go to a website and log in with NDC credentials rather than request the relevant spreadsheet from the holder. In addition to Ruby on Rails, I will be using JavaScript, CSS, and jQuery to help add functionality and ease of use to my web application. This web application will include a number of features that will help update and track progress on training. For example, one feature will be to track progress of a whole group of users to be able to see how the group as a whole is progressing. Another feature will be to assign tasks to either a user or a group of users. All of these together will create a user friendly and functional web application.