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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

A Case for Bundle Protocol in Space

NASA, through the Advanced Exploration Systems (AES) project, is investing in the development and infusion of delay tolerant networking (DTN) protocols for use on future space flight missions. The cornerstone of the DTN suite is the Bundle Protocol which provides network layer addressing and routing of data blocks. In 2017, the Plankton, Aerosol, Cloud, and Ocean Ecosystem (PACE) mission was selected as the first in-house robotic science mission to implement the Bundle Protocol for downlink of housekeeping telemetry. One year into the design and incorporation of the Bundle Protocol on PACE, this presentation makes a case for using the Bundle Protocol for communication with future space assets. Specifically, the use of the Bundle Protocol (1) simplifies relaying data through store and forward routing and custody transfer; (2) simplifies downlink management through delivery guarantees; and (3) simplifies storage services through block level interactions with memory devices.

Swinski, J. P.↗
NASA NTRS2010

Semi-Weekly Monitoring of the Performance and Attitude of Kepler Using a Sparse Set of Targets

The Kepler spacecraft is in a heliocentric Earth-trailing orbit, continuously observing ~160,000 select stars over ~115 square degrees of sky using its photometer containing 42 highly sensitive CCDs. The science data from these stars, consisting of ~6 million pixels at 29.4-minute intervals, is downlinked only every ~30 days. Additional low-rate Xband communications contacts are conducted with the spacecraft twice a week to downlink a small subset of the science data. This paper describes how we assess and monitor the performance of the photometer and the pointing stability of the spacecraft using such a sparse data set.

Attitude reconstruction↗
NASA NTRS2017

Multi-Beam Laser Beacon Propagation Over Lunar Distance: Comparison of Predictions and Measurements

A multi-beam beacon was transmitted from the Optical Communication Telescope Laboratory (OCTL) located at Table Mountain, CA to the Lunar Laser Space Terminal (LLST), on-board the Lunar Atmospheric Dust and Environment Explorer (LADEE) spacecraft, during NASA’s recent Lunar Laser Communication Demonstration (LLCD). The laser beacon (1568?0.1 nm) was square wave modulated and sensed by a LLST quadrant sensor to enable link acquisition and tracking. LLST computed the mean received beacon power and returned 5 kHz sampled power time series over the downlink. Post-processing of the decoded downlink received at OCTL retrieved the uplink power recorded at LLST. The predicted mean irradiance delivered to LLST consistently agreed with the variable beam divergence transmitted from OCTL to within < 1 decibel (dB). Irradiance fluctuations detected at LLST were reconciled with an uplink wave-propagation model derived using independently monitored atmospheric parameters. We report good agreement of the scintillation index and atmospheric coherence time.

Biswas, A↗
NASA NTRS2017

Status of NASA’s Deep Space Optical Communication Technology Demonstration

With NASA funding, the Deep Space Optical Communication (DSOC) Project at JPL is planning a system level technology demonstration of optical communications from deep space. A 22 cm diameter flight laser transceiver (FLT) is being developed for space flight. The FLT will be designed to transmit an average laser power of 4W at 1550 nm and receive a weak 1064 nm laser signal (> 100 femtowatts). Use of the Hale telescope at Palomar Mountain, CA, retrofitted with a photoncounting receiver to detect the downlink from space, is planned. The Optical Communication Telescope Laboratory (OCTL) at Table Mountain, CA will transmit a 1064 nm laser beacon to serve as a pointing reference for the FLT and support low-rate uplink data-rates. The DSOC FLT is part of the baseline payload for the Psyche mission spacecraft recently selected for flight by NASA, providing link demonstration opportunities during the mission cruise phase. Link demonstration opportunities at distances of approximately 0.1 to 2 astronomical units (AU) are expected. The DSOC system is being designed to support downlink data-rates of 0.2 to > 200 Mb/s and uplink data rates of approximately 1.6 kb/s. A status update of DSOC Project activities on flight and ground development will be summarized in this paper.

Biswas, Abhijit↗
NASA NTRS2016

The Adaptive Optics and Transmit System for NASA's Laser Communications Relay Demonstration Project

The Laser Communication Relay Demonstration is NASA’s multi-year demonstration of laser communication to a geosynchronous satellite. We are currently assembling the optical system for the first of the two baseline ground stations. The optical system consists of an adaptive optics system, the transmit system and a camera for target acquisition. The adaptive optics system is responsible for compensating the downlink beam for atmospheric turbulence and coupling it into the modem’s single mode fiber. The adaptive optics system is a woofer/tweeter design, with one deformable mirror correcting for low spatial frequencies with large amplitude and a second deformable mirror correcting for high spatial frequencies with small amplitude. The system uses a Shack-Hartmann wavefront sensor. The transmit system relays four beacon beams and one communication laser to the telescope for propagation to the space terminal. Both the uplink and downlink beams are centered at 1.55 microns. We present an overview of the design of the system as well as performance predictions including time series of coupling efficiency and expected uplink beam quality.

Laser Communication↗
NASA NTRS2017

Cassini Spacecraft Strategy for Recovering from a Complete Loss-Of-Signal Condition

Unlike other faults where the space craft’s automated Fault Protection (FP) routines can be relied upon to provide a carrier signal and telemetered data to the ground-based Spacecraft Operations Flight Support (SOFS) team to facilitate vehicle acquisition, diagnosis, and fault recovery, a complete Loss-of-Spacecraft-Signal (LOS) condition will yield no information at all to help re-acquire the vehicle and resolve the fault. For any FP response activation, the spacecraft’s downlink signal must be acquired via the Deep Space Network (DSN) on the expected (post-fault) Radio Frequency Subsystem (RFS) device configuration commanded by the FP; data that will not be attainable in the case of a complete LOS condition since there is no signal available for the ground station to lock onto. In the case of the Cassini Mission-to-Saturn spacecraft, numerous fault possibilities exist that can cause a LOS condition. Activations of the onboard RFS-related FP can reconfigure the post-fault RFS states, impeding the ground team’s ability to acquire the spacecraft’s downlink signal

Morgan, Paula S.↗
NASA NTRS2017

Juno Gravity Science: Preparing for Data Collection at Jupiter

One of the primary goals of the Juno mission is to investigate Jupiter’s interior by mapping its gravitational field with the gravity science instrument. The Juno spacecraft has two radio science components that comprise the gravity science instrument: the X-band telecommunications system for a X-up/X-down link and a Ka-band Translator for a Ka-up/Ka-down link. The Deep Space Network’s DSS-25 beam waveguide antenna at the Goldstone Deep Space Communications Complex in California provides the X- and Ka-band uplink alongside an Advanced Water Vapor Radiometer to calibrate tropospheric effects. X-band and Ka-band downlink data are collected with both open-loop and closed-loop receivers located at the complex. Utilization of Ka-band provides scientific benefit to the Doppler measurements, but also adds operational challenges. Pointing of the uplink and downlink Ka-band signals requires additional systems to be calibrated and operated by the Deep Space Network; and the higher frequency of Ka-band means the signal dynamics are increased by a factor of four over X-band signals. Due to the spacecraft’s elliptical orbit and 4000 kilometer perijove altitude, it accelerates at an extreme rate as it approaches Jupiter, inducing large dynamic ranges in Doppler range of approximately 6 MHz over 3 hours at Ka-band. After the installation of a new Ka-band transmitter at DSS-25 for Juno was completed in 2015, end-to-end testing was conducted to ensure readiness for operations at Jupiter and provide an initial assessment of the performance. Cruise testing was conducted in the same operational configuration that the system will be used in during perijove passes. Processed open-loop data yielded uncalibrated Doppler residuals of 1.9 mHz at X-band and 6.0 mHz at Ka-band with 5-second compression time. Conduction of these tests has prepared the instrument and the operations team for science data collection during the science phase of the mission.

Buccino, Dustin↗
NASA NTRS2016

Telemetry Ranging - Concept Paper Summary

Background - Previous CCSDS meetings: Spring 2015: Telemetry ranging technique was described; Fall 2015: A comparison to GMSK (Gaussian Minimum Shift Keying) plus PN (Pseudo-random Noise) ranging was made. -How telemetry ranging works: The spacecraft tracks the phase of the uplink PN ranging signal; Receive-time of downlink telemetry frame provides timing information; No downlink ranging signal is used. - This presentation: Summarizes the telemetry ranging concept paper. - Purpose: The purpose of the concept paper is to propose that the RFM (Radio Frequency Multiplier) Working Group consider telemetry ranging for inclusion as a recommended method for two-way ranging in the 401.0-B Blue Book.

Hamkins, Jon↗
NASA NTRS2019

ATLAS Flight Science Receiver Algorithms

This is the basis document for the ATLAS Receiver Algorithms. ATLAS is the single instrument on the ICESat-2 mission. The Receiver (Rx) Algorithms select the signal location in real-time and instruct the hardware to telemeter a vertical band of received time-tags about this signal location. The algorithms are implemented in the Flight Software (FSW) and in the hardware of the Photon Counting Electronics (PCE) cards. The sole purpose of the algorithms is to reduce the telemetry data volume to fit within the downlink constraint while maximizing the probability of downlinking surface signal. All versions of the Receiver Algorithms from version 2.8 onward incorporate our best knowledge of the ATLAS hardware at this time. It presents algorithms that, based on current Simulator testing, satisfy all of the requirements for the Rx Algorithms. Testing during ATLAS Instrument Integration and Testing with the hardware and software implementation of the Rx Algorithms revealed characteristics and responses that required changes to the Rx Algorithms and this document, which are captured in the change record below.All relevant documentation for the Receiver Algorithms can be found on the ICESat-2 Technical Data Management System (TDMS) under the ATLAS Algorithms subsystem.The launch version of the FSW (version 3.1.0) is based upon version 3.7c of this document.

Mcgarry, Jan L.↗
NASA NTRS2020

Event Selection and Background Rejection in Time Projection Chambers Using Convolutional Neural Networks and a Specific Application to the AdEPT Gamma-ray Polarimeter Mission

The Advanced Energetic Pair Telescope gamma-ray polarimeter uses a time projection chamber for measuring pair production events and is expected to generate a raw instrument data rate four orders of magnitude greater than is transmittable with typical satellite data communications. GammaNet, a convolutional neural network, proposes to solve this problem by performing event classification on-board for pair production and background events, reducing the data rate to a level that can be accommodated by typical satellite communication systems. In order to train GammaNet, a set of 1.1 × 10(exp 6) pair production events and 10(exp 6) background events were simulated for the Advanced Energetic Pair Telescope using the Geant4 Monte Carlo code. An additional set of 10(exp 6) pair production and 10 background events were simulated to test GammaNet’s capability for background discrimination. With optimization, GammaNet has achieved the proposed background rejection requirements for Galactic Cosmic Ray proton events. Given the best case assumption for downlink speeds, signal sensitivity for pair production ranged between 1.1 ± 0.5% to 69 ± 2% for 5 and 250 MeV incident gamma rays. This range became 0.1 ± 0.1% to 17 ± 2% for the worst case scenario of downlink speeds. The application of a feature visualization algorithm to GammaNet demonstrated decreased response to electronic noise and events exiting or entering the frame and increased response to parallel tracks that are close in proximity. GammaNet has been successfully implemented and shows promising results.

Richard L. Garnett↗
NASA NTRS1995

Incorporating CCSDS Telemetry Standards and Philosophy on Cassini

The Cassini project at the Jet Propulsion Laboratory (JPL) is implementing a spacecraft telemetry system based on the Consultative Committee for Space Data Systems (CCSDS) packet telemetry standards. Resolving the CCSDS concepts with a Ground Data System designed to handle time-division-multiplexed telemetry and also handling constraints unique to a deep-space planetary spacecraft (such as fixed downlink opportunities, small downlink rates and requirements for on-board data storage) have resulted in spacecraft and ground system design challenges. Solving these design challenges involved adapting and extending the CCSDS telemetry standards as well as changes to the spacecraft and ground system designs. The resulting spacecraft/ground system design is an example of how new ideas and philosophies can be incorporated into existing systems and design approaches without requiring significant rework. In addition, it shows that the CCSDS telemetry standards can be successfully applied to deep-space planetary spacecraft.

CCSDS↗
NASA NTRS2004

Intensity-based rock detection for acquiring onboard rover science

Missions to Mars already under study call for very long autonomous traverses (on the order of hundreds of meters per sol) during which there will be limited contact with Earth. The onboard Autonomous Science Investigation System (OASIS) is a technology for increasing science return during rover traverses by prioritizing science opportunities. By prioritizing data for downlink onboard, it is expected that the set of images selected for downlink by OASIS will have a consistently higher scientific interest then any set of equal number of images of the same traverse obtained using random or periodic sampling. Thus, OASIS can be used to increase the science returned from a long traverse. OASIS prioritizes data and identifies science opportunities by extracting information from image data and then using this information to prioritize the data and identify potential new science opportunities. Currently, the information extracted from the images is the location of the rocks in the image and several properties of these rocks such as size, albedo, texture and shape, In this paper we give an overview of the role of rock detection in the OASIS system and describe the functionality of the rock detector. We then present results on representative images

Judd, Michele↗
NASA NTRS2019

Telecommand/Telemetry Ranging for Deep-Space Applications

Conventional two-way pseudonoise (PN) ranging relies on measuring the time delay between a PN signal transmitted to the spacecraft, and a corresponding synchronized PN signal transmitted from the spacecraft and received on the ground. Recently, we introduced a two-way ranging method ([1], [2], [3]) which eliminates the need for the downlink PN ranging signal. In this telemetry ranging scheme, the requisite timing measurements are obtained from a databearing downlink telemetry signal. In the present paper, we extend the telemetry ranging concept by also eliminating the uplink PN signal, which is replaced by a data-bearing telecommand signal. We describe the architecture and concept of such a system, and describe the fundamental limitations of tracking the timing of such uplink telecommand signals when tracking loops or demod-remod correlation techniques are employed. An end-to-end performance analysis shows that in typical scenarios, ranging performance comparable to conventional PN ranging is possible.

Hamkins, Jon↗
NASA NTRS2017

Horizon Detection for Mars Surface Operations

A new image processing method for automated horizon detection is presented in this paper. This method was developed for the Mars Exploration Rovers mission’s surface operations to aid in determining orbiter visibility periods for downlink data, and is now being considered for all Mars surface missions and for a variety of applications. Starting with images received from Mars rovers or landers, the horizon pixel location is found by (1) obtaining the gradient images using the Sobel operator, (2) calculating the preliminary horizon locations by optimizing the maximum difference between sky and ground regions in the gradient domain, and (3) applying a multi-variable thresholding method. The results are analyzed using a variety of images from the Mars rovers, as an example one dataset’s results were categorized as 94.2% Good, 4.11% Okay, and 1.65% Poor. The pixel location corresponding to the found horizon in an image is converted to azimuth and elevation values using the camera model. The elevation of the terrain surrounding the rover or lander directly affects the duration orbiters are visible for downlink data volume, and when the sun is visible for image quality or solar energy consumption. Having an automated process to detect the elevation of the terrain allows the operation team to better predict the outcome of the plan, reducing heath and safety risks and allowing new operational limits to be defined.

Oij, Stephanie Lynn↗
NASA NTRS2017

Calibration and Performance Measurements for the NASA Deep Space Network Aperture Enhancement Project (DAEP)

The NASA Deep Space Network (DSN) has recently constructed two new 34-meter antennas at the Canberra Deep Space Communications Complex (CDSCC). These new antennas are part of the larger DAEP project to add six new 34-meter antennas to the DSN, including two in Madrid, three in Canberra and one in Goldstone (California). The DAEP project included development and implementation of several new technologies for the S, X, Ka (26 GHz) and Ka (32 GHz) -band uplink and downlink electronics, as previously reported. The electronics upgrades were driven by several different considerations, including parts obsolescence, cost reduction, improved reliability and maintainability, and capability to meet future performance requirements. The new antennas are required to support TT&C links for all of the NASA deep-space spacecraft, as well as for several international partners. Some of these missions, such as Voyager 1 and 2, have very limited link budgets, which results in demanding requirements for system G/T performance. These antennas are also required to support radio science missions with several spacecraft, which dictate some demanding requirements for spectral purity, amplitude stability and phase stability for both the uplink and downlink electronics. After completion of these upgrades, a comprehensive campaign of tests and measurements took place to characterize the electronics and calibrate the antennas. Radiometric measurement techniques were applied to characterize, calibrate, and optimize the performance of the antenna parameters. These included optical and RF high-resolution holographic and total power radiometry techniques. These techniques, which are described in the article, resulted in the highest antenna aperture efficiency in the DSN, of 66% achieved, at the highest operating frequency of the antenna, which is Ka-Band (32-GHz). The other measurements and results described include antenna noise temperature, photogrammetry and holography alignment of antenna panels, beam-waveguide mirrors, and subreflector, antenna aperture efficiencies and G/T versus frequency, and antenna pointing models. The first antenna (DSS-35) was entered into operations in October, 2014 and the 2nd antenna (DSS-36) in October, 2016. This paper describes the measurement techniques and results of the testing and calibration for both antennas, along with the driving requirements.

Rochblatt, David J.↗
NASA NTRS2018

RESTful CFDP: Managing GDS Complexity with Microservices

NASA's Advanced Multi-Mission Operations System (AMMOS) is currently adding capability to support the CCSDS File Delivery Protocol (CFDP). This feature is being added as part of the AMMOS Mission Data Processing and Control System (AMPCS). In order to address the system’s increasing complexity, AMPCS has recently been re-architected to break down its monolithic applications into smaller, individually deployable microservices. The CFDP capability is the first new AMPCS feature to leverage this new architecture. The CFDP microservice provides a web-based Representational State Transfer (REST) application programming interface (API) for complete monitor and control of its operations, and this enables it to be decoupled from other AMPCS microservices. This also results in better scalability for redundancy and load balancing. AMPCS's CFDP microservice is designed to support generic CFDP operations, agnostic to AMPCS's legacy concept of Downlink Products. An optional runtime plug-in allows the CFDP microservice to simulate CFDP artifacts as Downlink Products. Applying the microservices software architecture pattern both in the latest release of AMPCS and in providing the new CFDP capability has resulted in a more flexible system with improved extensibility and maintainability. System complexity has also become more manageable.

Choi, Joshua S.↗
NASA NTRS2018

Multiple Uplinks Per Antenna (MUPA) Signal Acquisition Schemes

The Deep Space Network (DSN) currently makes use of the technique of Multiple Spacecraft per Antenna (MSPA) where a single antenna is used to track multiple spacecraft downlinks within its beam, such as in the case of multiple spacecraft orbiting Mars at 8.4 GHz (X-band). It is desired to extend this technique to the uplink where a single station is used to send a signal to multiple spacecraft in order to make more efficient use of ground resources. This would be applicable to numerous smallsat constellations being considered for future missions or to future spacecraft at Venus, Mars, or more distant destinations that are all within the half-power beamwidth of a single 34-m diameter antenna. In one scheme, each spacecraft’s command sequences would be time multiplexed onto a single uplink frequency. Each spacecraft would lock onto the uplink signal and would accept only commands intended for it via special identifier codes. Each spacecraft would also emit a downlink signal to the ground that is coherent with the uplink signal but would have its own allocated frequency channel and identifier information. A couple of key challenges associated with using this technique need to be addressed. Because of the single uplink frequency, coherent turnaround for two-way Doppler and ranging would not conform to established ratios, thus the radios employed by the spacecraft would need to be capable of variable turnaround ratios. In addition, because of the different orbits or spacecraft trajectories, the relative Doppler shifts and rates can be large with respect to the common uplink signal whose frequency would lie at the centroid of the frequencies of the expected received signals of the constellation. This would be problematic with standard analog spacecraft radios whose acquisition bandwidths are relatively small (~1.7 kHz) relative to the large frequency offsets (~100 kHz) expected using the single frequency uplink technique. With the advent of software defined radios (SDRs), signal frequency search algorithms can be utilized within the flight software and/or programmable hardware (e.g., FPGAs) that can easily acquire and track signals with large frequency offsets and varying dynamics. Such techniques could include FFT search algorithms, step-and-sweep search algorithms, or onboard frequency steering making use of trajectory vectors uplinked to each member spacecraft. Other challenges include mitigation of potential interference between received signals. We have identified several software defined radios that are in different stages of development and whose key parameters have been tabulated. We have examined each radio’s capabilities with respect to acquiring and tracking signals with large frequency offsets. Such analyses made use of previous studies supplemented with specially designed tests using both simulation tools and/or existing testbeds. We have compared signal acquisition times computed from provided algorithms along with measured values derived from tests using existing hardware and simulation tools for the purpose of conducting tradeoff studies between the various radio designs and software/firmware programming approaches.

Abraham, Douglas S.↗