Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172443
Koki Tanaka, M. Spenko
This paper describes the experimental evaluation of a robotic gripper's ability to perch on a variety of flat surfaces when used in conjunction with a free-flying robot in microgravity. The gripper is designed to be integrated with Astrobee, a free-flying robot deployed in the International Space Station (ISS) in April 2019. Astrobee was developed to help astronauts perform routine tasks while aboard the ISS. The robot has physical space for payloads such as a manipulator arm, which allows it to grasp grapple points such as handrails to conserve energy while maintaining a given position. However, grapple points are not always readily available. As such, the goal of this work is to have Astrobee perch onto other surfaces. To enable extended perching times, the gripper described here uses a gecko-like/electrostatic adhesive coupled with a cam-actuated mechanism designed to consume little to no energy while engaged with a surface. The gecko-like adhesives allow the gripper to easily attach and detach to/from surfaces through the camactuation mechanism. The gripper was tested in a simulated microgravity environment where it was mounted on a platform equipped with air bearings. This paper describes the gripper design and evaluates the gripper's attachment performance as a function of the platform's approach velocity and approach angle for several different target material types. The gripper perched on glass and acrylic substrates with over a 70% success rate. For carbon fiber/epoxy laminate and Kapton sheets the success rate was approximately 50%. The results showed a clear correlation between the approach velocity and approach angle for carbon and glass materials.
{"title":"A Gecko-Like/Electrostatic Gripper for Free-Flying Perching Robots","authors":"Koki Tanaka, M. Spenko","doi":"10.1109/AERO47225.2020.9172443","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172443","url":null,"abstract":"This paper describes the experimental evaluation of a robotic gripper's ability to perch on a variety of flat surfaces when used in conjunction with a free-flying robot in microgravity. The gripper is designed to be integrated with Astrobee, a free-flying robot deployed in the International Space Station (ISS) in April 2019. Astrobee was developed to help astronauts perform routine tasks while aboard the ISS. The robot has physical space for payloads such as a manipulator arm, which allows it to grasp grapple points such as handrails to conserve energy while maintaining a given position. However, grapple points are not always readily available. As such, the goal of this work is to have Astrobee perch onto other surfaces. To enable extended perching times, the gripper described here uses a gecko-like/electrostatic adhesive coupled with a cam-actuated mechanism designed to consume little to no energy while engaged with a surface. The gecko-like adhesives allow the gripper to easily attach and detach to/from surfaces through the camactuation mechanism. The gripper was tested in a simulated microgravity environment where it was mounted on a platform equipped with air bearings. This paper describes the gripper design and evaluates the gripper's attachment performance as a function of the platform's approach velocity and approach angle for several different target material types. The gripper perched on glass and acrylic substrates with over a 70% success rate. For carbon fiber/epoxy laminate and Kapton sheets the success rate was approximately 50%. The results showed a clear correlation between the approach velocity and approach angle for carbon and glass materials.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126104414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172481
Hady Benyamen, Aaron McKinnis, S. Keshmiri
In this paper, the propwash phenomenon for pusher configuration unmanned aerial systems (UASs) is studied. The SkyHunter UAS has the propeller placed aft of the fuselage and in front of the horizontal tail with no offset from the zero lift plane. Thus, the propeller slipstream directly flows over the horizontal tail affecting its aerodynamics. To validate the physics based model developed for propwash impacts and to quantify the effects of propwash, the SkyHunter UAS was equipped with an extra pitot tube. The first pitot tube was placed at the nose of the aircraft where the air is undisturbed and it was measuring the aircraft's velocity. The second pitot tube was placed at different locations on the horizontal tail and three flight tests were conducted. Flight test data showed that the current configuration of the SkyHunter: (A) has large variations in the horizontal tail dynamic pressure ratio along the span of the horizontal tail. (B) had the dynamic pressure ratio higher than 1.7 in two of the three investigated locations along the span of the horizontal tail. This suggests that the theoretical estimate of the dynamic pressure ratio (which is 0.93) may be an under estimation. (C) The dynamic pressure ratio varied with time during flight. A change in the horizontal tail dynamic pressure ratio directly leads to a shift in the location of the aerodynamic center of an aircraft as well as changes in the stability and control derivatives of an aircraft. The implication of these changes in small UASs can be significant since they affect the aircraft longitudinal stability, trim elevator, and flight characteristics. In order to mitigate such changes during flight, a redesign was made to the original empennage design where is an offset was added between the zero lift plane and the aerodynamic center of the horizontal tail. This redesign intends to move the horizontal tail above (and away from) the propeller slipstream. Manufacturing of the redesigned horizontal tail was completed recently and it was flight tested. Flight test data from the new design show that the new design successfully mitigates the effects of the propwash.
{"title":"Effects of Propwash on Horizontal Tail Aerodynamics of Pusher UASs","authors":"Hady Benyamen, Aaron McKinnis, S. Keshmiri","doi":"10.1109/AERO47225.2020.9172481","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172481","url":null,"abstract":"In this paper, the propwash phenomenon for pusher configuration unmanned aerial systems (UASs) is studied. The SkyHunter UAS has the propeller placed aft of the fuselage and in front of the horizontal tail with no offset from the zero lift plane. Thus, the propeller slipstream directly flows over the horizontal tail affecting its aerodynamics. To validate the physics based model developed for propwash impacts and to quantify the effects of propwash, the SkyHunter UAS was equipped with an extra pitot tube. The first pitot tube was placed at the nose of the aircraft where the air is undisturbed and it was measuring the aircraft's velocity. The second pitot tube was placed at different locations on the horizontal tail and three flight tests were conducted. Flight test data showed that the current configuration of the SkyHunter: (A) has large variations in the horizontal tail dynamic pressure ratio along the span of the horizontal tail. (B) had the dynamic pressure ratio higher than 1.7 in two of the three investigated locations along the span of the horizontal tail. This suggests that the theoretical estimate of the dynamic pressure ratio (which is 0.93) may be an under estimation. (C) The dynamic pressure ratio varied with time during flight. A change in the horizontal tail dynamic pressure ratio directly leads to a shift in the location of the aerodynamic center of an aircraft as well as changes in the stability and control derivatives of an aircraft. The implication of these changes in small UASs can be significant since they affect the aircraft longitudinal stability, trim elevator, and flight characteristics. In order to mitigate such changes during flight, a redesign was made to the original empennage design where is an offset was added between the zero lift plane and the aerodynamic center of the horizontal tail. This redesign intends to move the horizontal tail above (and away from) the propeller slipstream. Manufacturing of the redesigned horizontal tail was completed recently and it was flight tested. Flight test data from the new design show that the new design successfully mitigates the effects of the propwash.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123275355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172453
Elizabeth Harkavy, M. S. Net
In order to effectively communicate with Earth from deep space there is a need for network automation similar to that of the Internet. The existing automated network protocols, such as TCP and IP, cannot work in deep space due to the assumptions under which they were designed. Specifically, protocols assume the existence of an end-to-end path between the source and destination for the entirety of a communication session and the path being traversable in a negligible amount of time. In contrast, a Delay Tolerant Network is a set of protocols that allows networking in environments where links suffer from high-delay or disruptions (e.g. Deep Space). These protocols rely on different assumptions such as time synchronization and suitable memory allocation. In this paper, we consider the problem of autonomously avoiding memory overflows in a Delay Tolerant Node. To that end, we propose using Reinforcement Learning to automate buffer management given that we can easily measure the relative rates of data coming in and out of the DTN node. In the case of detecting overflow, we let the autonomous agent choose between three actions: slowing down the client, requesting more resources from the Deep Space Network, or selectively dropping packets once the buffer nears capacity. Furthermore, we show that all of these actions can be realistically implemented in real-life operations given current and planned capabilities of Delay Tolerant Networking and the Deep Space Network. Similarly, we also show that using Reinforcement Learning for this problem is well suited to this application due to the number of possible states and variables, as well as the fact that large distances between deep space spacecraft and Earth prevent human-in-the-loop intervention.
{"title":"Utilizing Reinforcement Learning to Autonomously Mange Buffers in a Delay Tolerant Network Node","authors":"Elizabeth Harkavy, M. S. Net","doi":"10.1109/AERO47225.2020.9172453","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172453","url":null,"abstract":"In order to effectively communicate with Earth from deep space there is a need for network automation similar to that of the Internet. The existing automated network protocols, such as TCP and IP, cannot work in deep space due to the assumptions under which they were designed. Specifically, protocols assume the existence of an end-to-end path between the source and destination for the entirety of a communication session and the path being traversable in a negligible amount of time. In contrast, a Delay Tolerant Network is a set of protocols that allows networking in environments where links suffer from high-delay or disruptions (e.g. Deep Space). These protocols rely on different assumptions such as time synchronization and suitable memory allocation. In this paper, we consider the problem of autonomously avoiding memory overflows in a Delay Tolerant Node. To that end, we propose using Reinforcement Learning to automate buffer management given that we can easily measure the relative rates of data coming in and out of the DTN node. In the case of detecting overflow, we let the autonomous agent choose between three actions: slowing down the client, requesting more resources from the Deep Space Network, or selectively dropping packets once the buffer nears capacity. Furthermore, we show that all of these actions can be realistically implemented in real-life operations given current and planned capabilities of Delay Tolerant Networking and the Deep Space Network. Similarly, we also show that using Reinforcement Learning for this problem is well suited to this application due to the number of possible states and variables, as well as the fact that large distances between deep space spacecraft and Earth prevent human-in-the-loop intervention.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"129 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123602867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172795
SeyyedPooya HekmatiAthar, N. Goudarzi, A. Karimoddini, A. Homaifar, Darshan Divakaran
Unmanned Aerial System (UAS)-enabled bridge inspection technique, as a promising alternative to conventional practices, has drawn more interest in recent years. However, UAS performance metrics requirements imposed by bridge structure (e.g., turbulent flow characteristics around the bridge) and terrain characteristics (e.g., surface roughness, temperature, and humidity), have made the selection of the suitable UAS platform a challenging problem. Currently, there is no verified and comprehensive methodology for UAS-enabled bridge inspection practices; existing case-dependent solutions rely on general-purpose commercially available UAS platforms. There is no study to quantify the gap between the performance metrics of the commercially available UAS platforms to those required for the bridge inspection. The objective of this paper is to initiate the development of a framework to systematically select a commercially available UAS that is the most appropriate choice for bridge inspection. An Analytic Hierarchy Process (AHP) methodology is adopted for the multiple-criteria decision making (MCDM) and comparing the capabilities of multiple UAS platforms. The AHP methodology is applied to 32 criteria defined under Four major categories including flight performance, situational awareness, payload and sensor capabilities, and communication quality. The developed method is illustrated and applied to a set of UAS platforms. A pairwise comparison approach is conducted in a hierarchical manner at the category level, criterion level, and candidate platform level. The results from comparison tables that meet the required AHP consistency ratio threshold, result in the selection of the most suitable UAS for bridge inspection in the defined scenario.
{"title":"A systematic evaluation and selection of UAS-enabled solutions for bridge inspection practices","authors":"SeyyedPooya HekmatiAthar, N. Goudarzi, A. Karimoddini, A. Homaifar, Darshan Divakaran","doi":"10.1109/AERO47225.2020.9172795","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172795","url":null,"abstract":"Unmanned Aerial System (UAS)-enabled bridge inspection technique, as a promising alternative to conventional practices, has drawn more interest in recent years. However, UAS performance metrics requirements imposed by bridge structure (e.g., turbulent flow characteristics around the bridge) and terrain characteristics (e.g., surface roughness, temperature, and humidity), have made the selection of the suitable UAS platform a challenging problem. Currently, there is no verified and comprehensive methodology for UAS-enabled bridge inspection practices; existing case-dependent solutions rely on general-purpose commercially available UAS platforms. There is no study to quantify the gap between the performance metrics of the commercially available UAS platforms to those required for the bridge inspection. The objective of this paper is to initiate the development of a framework to systematically select a commercially available UAS that is the most appropriate choice for bridge inspection. An Analytic Hierarchy Process (AHP) methodology is adopted for the multiple-criteria decision making (MCDM) and comparing the capabilities of multiple UAS platforms. The AHP methodology is applied to 32 criteria defined under Four major categories including flight performance, situational awareness, payload and sensor capabilities, and communication quality. The developed method is illustrated and applied to a set of UAS platforms. A pairwise comparison approach is conducted in a hierarchical manner at the category level, criterion level, and candidate platform level. The results from comparison tables that meet the required AHP consistency ratio threshold, result in the selection of the most suitable UAS for bridge inspection in the defined scenario.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126628853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172672
M. Chodas, R. Masterson, O. de Weck
When developing a space system, many properties of the design space are initially unknown and are discovered during the development process. Therefore, the problem exhibits deep uncertainty. Deep uncertainty refers to the condition where the full range of outcomes of a decision is not knowable. A key strategy to mitigate deep uncertainty is to update decisions when new information is learned. In this paper, the spacecraft development problem is modeled as a dynamic, chance-constrained, stochastic optimization problem. The Model-based Adaptive Design under Uncertainty (MADU) framework is presented, in which conflict-directed search is combined with reuse of information to solve the development problem efficiently in the presence of deep uncertainty. The framework is built within a Model-based Systems Engineering (MBSE) paradigm in which a SysML model contains the design, the design space, and information learned during search. The development problem is composed of a series of optimizations, each different than the previous. Changes between optimizations can be the addition or removal of a design variable, expansion or contraction of the domain of a design variable, addition or removal of constraints, or changes to the objective function. These changes are processed to determine which search decisions can be preserved from the previous optimization. The framework is illustrated on a case study drawn from the thermal design of the REgolith X-ray Imaging Spectrometer (REXIS) instrument. This case study demonstrates the advantages of the MADU framework with the solution found 30% faster than an algorithm that doesn't reuse information. With this framework, designers can more efficiently explore the design space and perform updates to a design when new information is learned. Future work includes extending the framework to multiple objective functions and continuous design variables.
{"title":"Addressing Deep Uncertainty in Space System Development through Model-based Adaptive Design","authors":"M. Chodas, R. Masterson, O. de Weck","doi":"10.1109/AERO47225.2020.9172672","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172672","url":null,"abstract":"When developing a space system, many properties of the design space are initially unknown and are discovered during the development process. Therefore, the problem exhibits deep uncertainty. Deep uncertainty refers to the condition where the full range of outcomes of a decision is not knowable. A key strategy to mitigate deep uncertainty is to update decisions when new information is learned. In this paper, the spacecraft development problem is modeled as a dynamic, chance-constrained, stochastic optimization problem. The Model-based Adaptive Design under Uncertainty (MADU) framework is presented, in which conflict-directed search is combined with reuse of information to solve the development problem efficiently in the presence of deep uncertainty. The framework is built within a Model-based Systems Engineering (MBSE) paradigm in which a SysML model contains the design, the design space, and information learned during search. The development problem is composed of a series of optimizations, each different than the previous. Changes between optimizations can be the addition or removal of a design variable, expansion or contraction of the domain of a design variable, addition or removal of constraints, or changes to the objective function. These changes are processed to determine which search decisions can be preserved from the previous optimization. The framework is illustrated on a case study drawn from the thermal design of the REgolith X-ray Imaging Spectrometer (REXIS) instrument. This case study demonstrates the advantages of the MADU framework with the solution found 30% faster than an algorithm that doesn't reuse information. With this framework, designers can more efficiently explore the design space and perform updates to a design when new information is learned. Future work includes extending the framework to multiple objective functions and continuous design variables.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126956608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172288
Job M. Champagne, D. Carver
Software systems have become ubiquitous in today's world. Most software will evolve after initial deployment. Software changes that are a part of that evolution often are documented in a requirements change document. One of the challenges when changing software is understanding the portions of the existing requirements and the existing code that could be affected by the change in order to avoid or minimize unexpected side effects from the changes. Researchers have addressed the problem of minimizing the effect of changes by using different methods, including text mining and clustering. Some approaches to determine change impact are based on information retrieval (IR) techniques using both term frequency-inverse document frequency (TF—IDF) and latent semantic indexing (LSI) methods. Other approaches are based on visualization techniques using degree and betweenness centrality measures. In this research, we approach the problem by applying IR techniques along with data mining. We apply TF-IDF and LSI to investigate which changes have a high potential of modifying existing requirements. We also analyze similarities between changes that do not map to existing requirements. In both cases, our threshold for identifying similarity is 80%. We designed our approach to identify, for a given change, one or more requirements that have a high potential of being associated with the change as well as identifying intra-document requirements or changes that have a high potential for consolidation. We were able to identify requirements that had a similarity of at least 80% to a change request using TF-IDF and LSI. We were also able to isolate changes that did not show a high similarity to any requirement, thus indicating that the change request was likely a request for a new requirement. The results are encouraging for assessing the impact of software change requests on requirements of an existing system.
{"title":"Discovering Relationships Among Software Artifacts","authors":"Job M. Champagne, D. Carver","doi":"10.1109/AERO47225.2020.9172288","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172288","url":null,"abstract":"Software systems have become ubiquitous in today's world. Most software will evolve after initial deployment. Software changes that are a part of that evolution often are documented in a requirements change document. One of the challenges when changing software is understanding the portions of the existing requirements and the existing code that could be affected by the change in order to avoid or minimize unexpected side effects from the changes. Researchers have addressed the problem of minimizing the effect of changes by using different methods, including text mining and clustering. Some approaches to determine change impact are based on information retrieval (IR) techniques using both term frequency-inverse document frequency (TF—IDF) and latent semantic indexing (LSI) methods. Other approaches are based on visualization techniques using degree and betweenness centrality measures. In this research, we approach the problem by applying IR techniques along with data mining. We apply TF-IDF and LSI to investigate which changes have a high potential of modifying existing requirements. We also analyze similarities between changes that do not map to existing requirements. In both cases, our threshold for identifying similarity is 80%. We designed our approach to identify, for a given change, one or more requirements that have a high potential of being associated with the change as well as identifying intra-document requirements or changes that have a high potential for consolidation. We were able to identify requirements that had a similarity of at least 80% to a change request using TF-IDF and LSI. We were also able to isolate changes that did not show a high similarity to any requirement, thus indicating that the change request was likely a request for a new requirement. The results are encouraging for assessing the impact of software change requests on requirements of an existing system.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115182234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172616
D. Buccino, M. Soriano, K. Oudrhiri, S. Finley, D. Kahan, O. Yang, A. Jongeling
Since launch, radio science has been a key component of the Juno mission to Jupiter. The prime objective of the radio science investigation is to estimate the gravitational field of Jupiter from the Doppler shift on the radio link between the spacecraft and the Earth-based observing antennas of NASA's Deep Space Network (DSN). In addition to estimation of the gravitational field, radio science has provided critical engineering support to the Juno mission. Utilizing high-sensitivity open-loop receivers and real-time signal processing, radio science is able to detect the ‘heartbeat’ of the Juno spacecraft and determine the current state of the spacecraft. The Juno spacecraft utilizes two frequencies for communication with Earth: the telecommunications system X-band link and the radio science Ka-band link. Radio science has provided communications monitoring support for the spacecraft launch in 2011, spacecraft main engine firings (including Deep Space Maneuvers in 2012 and Jupiter Orbit Insertion in 2016), the Earth gravity assist flyby in 2013, and times when the spacecraft was off-Earth point during Jupiter closest approach with a weak signal level. By measuring the signal-to-noise ratio, received carrier frequency, and subcarrier frequency of the X-band downlink signal in real-time, radio science is able to determine the state of the spacecraft in scenarios where the link margin is not sufficient to support telemetry. An off-nominal spacecraft state will change the signal-to-noise level, subcarrier frequency, and spin modulation of the carrier frequency which are detectable in the open-loop receiver of the DSN. With the addition of multiple frequency shift keying (MFSK) ‘tones’ encoding, the subcarrier frequency can be changed onboard the spacecraft for determination of selected events by the flight team. Tones were utilized during main engine firings on Juno, including Jupiter Orbit Insertion (JOI). Tones are decoded in near real-time by the Entry, Descent, and Landing (EDL) Data Analysis (EDA) system downstream of the DSN open-loop receivers. Robust implementation of hardware, software, and operations planning has ensured successful data collection and real-time status reporting of spacecraft state to the Juno mission. Lessons learned from communicating with Juno in this way while in the harsh environment of Jupiter are documented and discussed in the context of upcoming missions to Jupiter.
{"title":"Detecting Juno's ‘Heartbeat’: Communications Support during Critical Events of the Juno Mission","authors":"D. Buccino, M. Soriano, K. Oudrhiri, S. Finley, D. Kahan, O. Yang, A. Jongeling","doi":"10.1109/AERO47225.2020.9172616","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172616","url":null,"abstract":"Since launch, radio science has been a key component of the Juno mission to Jupiter. The prime objective of the radio science investigation is to estimate the gravitational field of Jupiter from the Doppler shift on the radio link between the spacecraft and the Earth-based observing antennas of NASA's Deep Space Network (DSN). In addition to estimation of the gravitational field, radio science has provided critical engineering support to the Juno mission. Utilizing high-sensitivity open-loop receivers and real-time signal processing, radio science is able to detect the ‘heartbeat’ of the Juno spacecraft and determine the current state of the spacecraft. The Juno spacecraft utilizes two frequencies for communication with Earth: the telecommunications system X-band link and the radio science Ka-band link. Radio science has provided communications monitoring support for the spacecraft launch in 2011, spacecraft main engine firings (including Deep Space Maneuvers in 2012 and Jupiter Orbit Insertion in 2016), the Earth gravity assist flyby in 2013, and times when the spacecraft was off-Earth point during Jupiter closest approach with a weak signal level. By measuring the signal-to-noise ratio, received carrier frequency, and subcarrier frequency of the X-band downlink signal in real-time, radio science is able to determine the state of the spacecraft in scenarios where the link margin is not sufficient to support telemetry. An off-nominal spacecraft state will change the signal-to-noise level, subcarrier frequency, and spin modulation of the carrier frequency which are detectable in the open-loop receiver of the DSN. With the addition of multiple frequency shift keying (MFSK) ‘tones’ encoding, the subcarrier frequency can be changed onboard the spacecraft for determination of selected events by the flight team. Tones were utilized during main engine firings on Juno, including Jupiter Orbit Insertion (JOI). Tones are decoded in near real-time by the Entry, Descent, and Landing (EDL) Data Analysis (EDA) system downstream of the DSN open-loop receivers. Robust implementation of hardware, software, and operations planning has ensured successful data collection and real-time status reporting of spacecraft state to the Juno mission. Lessons learned from communicating with Juno in this way while in the harsh environment of Jupiter are documented and discussed in the context of upcoming missions to Jupiter.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116424122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172778
M. S. Net, K. Cheung
NASA's human exploration program is currently working towards landing astronauts on the surface of the Moon by 2024, close the lunar South Pole. To guarantee astronaut safety and maximize science data return, NASA is in the process of defining the communication architecture that will support all astronaut activities from launch to surface operations. Of particular interest to this paper are links from the lunar surface back to Earth without any intermediate relays. We show that the system geometry is such that antennas on the landing system will need to be pointed at low elevation angles, thus potentially causing multi-path fading effects not typically encountered in space communications. This paper is organized in three parts. First, we characterize the multi-path fading effects expected in links between the lunar South Pole and Earth and show that for moderate data rates (less than 1 Mbps) the links suffer from slow fading. We then show that for this operations regime the performance of forward error correction schemes is significantly worse for traditional Additive White Gaussian Noise channels. Finally, we investigate multi-copy mechanisms to mitigate the effects of fading, most notably repetition schemes and Automatic Repeat Request.
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Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172636
D. Lasi, R. de Neufville
The emergence of new small launchers for 100–250 kg satellite payloads makes the case for new space launch complexes that can support the future growing demand for launches of satellite constellations. However, development timeline and architecture of new launchers, as well as launch demand, are uncertain. Therefore, there is great uncertainty about the economic viability of any specific design for the development of new launch infrastructure projects. This study demonstrates how flexible design of the launch facility can increase the financial feasibility of new launch infrastructure projects. We do this by comparing the economic performance of fixed and flexible designs, considering uncertainties about the type of launchers that will succeed on the markets, their development time, and the launch demand. The infrastructure is hypothetically located in Europe, where there is a high uncertainty about the future emergence of new launchers. The fixed, inflexible designs involve upfront decisions to realize launches using a single propellant (solid, liquid, or hybrid). The flexible design invests only in a minimal set of initial flexible facilities that can support various propellants, while holding the option to add later propellant-specific infrastructure. The economic analysis applies Monte Carlo simulation to a spreadsheet of the discounted cash flows of revenues and expenses over the life to the project. This leads to estimates of the distribution of both Expected Net Present Value (ENPV) and the 5% Value at Risk (VAR) of the project. The results show that the flexible design has the highest VAR, because acquiring flexibility is costly as it requires to design after a superset of requirements; however, while all projects have a negative ENPV, the flexible design outperforms the inflexible designs on average, and dominates the inflexible designs if one considers the incentives of both the public and private parts in a hypothetical public-private partnership.
{"title":"Flexible Design Opportunities in Small-Satellites Launch Infrastructures","authors":"D. Lasi, R. de Neufville","doi":"10.1109/AERO47225.2020.9172636","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172636","url":null,"abstract":"The emergence of new small launchers for 100–250 kg satellite payloads makes the case for new space launch complexes that can support the future growing demand for launches of satellite constellations. However, development timeline and architecture of new launchers, as well as launch demand, are uncertain. Therefore, there is great uncertainty about the economic viability of any specific design for the development of new launch infrastructure projects. This study demonstrates how flexible design of the launch facility can increase the financial feasibility of new launch infrastructure projects. We do this by comparing the economic performance of fixed and flexible designs, considering uncertainties about the type of launchers that will succeed on the markets, their development time, and the launch demand. The infrastructure is hypothetically located in Europe, where there is a high uncertainty about the future emergence of new launchers. The fixed, inflexible designs involve upfront decisions to realize launches using a single propellant (solid, liquid, or hybrid). The flexible design invests only in a minimal set of initial flexible facilities that can support various propellants, while holding the option to add later propellant-specific infrastructure. The economic analysis applies Monte Carlo simulation to a spreadsheet of the discounted cash flows of revenues and expenses over the life to the project. This leads to estimates of the distribution of both Expected Net Present Value (ENPV) and the 5% Value at Risk (VAR) of the project. The results show that the flexible design has the highest VAR, because acquiring flexibility is costly as it requires to design after a superset of requirements; however, while all projects have a negative ENPV, the flexible design outperforms the inflexible designs on average, and dominates the inflexible designs if one considers the incentives of both the public and private parts in a hypothetical public-private partnership.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122782583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-01DOI: 10.1109/AERO47225.2020.9172445
R. Merl, Elaine Cox, Richard Dutch, P. Graham, Sam Larsen, J. Michel, D. Milby, K. Morgan, K. Tripp
The Advanced Processing and Communications team at Los Alamos National Laboratory has designed and manufactured a new system controller that complies with the 6U SpaceVPX (ANSI/VITA 78) specification and can function as a command- and data-handling single-board computer. The design meets the radiation hardness requirements for application in geosynchronous (GEO) and medium earth orbit (MEO), employs QMLV and Class-S components, has a conduction cooling frame, and is mechanically hardened against typical shock and vibration profiles encountered during launch. The system controller is based on the space grade GR740 quadcore LEON4 processor ASIC with a MicroChip RTG4 field programmable gate array (FPGA) to support hardware coprocessing and supply the gigabit /s serializer-deserializers (SerDes) needed for the VPX control and data planes. This module was designed to allow interoperability between OpenVPX (ANSI/VITA 65) and SpaceVPX so that lower cost hardware from the commercial world can be used during the prototyping process instead of more expensive flight like hardware. This design has 1 GByte of SDRAM with an additional ½ GByte of error detection and correction memory (EDAC). Since SDRAM is susceptible to single event functional interrupts (SEFIs), the design team used byte-wide aspect ratio memories with individual power control for recovery. This paper will discuss the performance, power consumption, and status of this design.
{"title":"LEON4 Based Radiation-Hardened SpaceVPX System Controller","authors":"R. Merl, Elaine Cox, Richard Dutch, P. Graham, Sam Larsen, J. Michel, D. Milby, K. Morgan, K. Tripp","doi":"10.1109/AERO47225.2020.9172445","DOIUrl":"https://doi.org/10.1109/AERO47225.2020.9172445","url":null,"abstract":"The Advanced Processing and Communications team at Los Alamos National Laboratory has designed and manufactured a new system controller that complies with the 6U SpaceVPX (ANSI/VITA 78) specification and can function as a command- and data-handling single-board computer. The design meets the radiation hardness requirements for application in geosynchronous (GEO) and medium earth orbit (MEO), employs QMLV and Class-S components, has a conduction cooling frame, and is mechanically hardened against typical shock and vibration profiles encountered during launch. The system controller is based on the space grade GR740 quadcore LEON4 processor ASIC with a MicroChip RTG4 field programmable gate array (FPGA) to support hardware coprocessing and supply the gigabit /s serializer-deserializers (SerDes) needed for the VPX control and data planes. This module was designed to allow interoperability between OpenVPX (ANSI/VITA 65) and SpaceVPX so that lower cost hardware from the commercial world can be used during the prototyping process instead of more expensive flight like hardware. This design has 1 GByte of SDRAM with an additional ½ GByte of error detection and correction memory (EDAC). Since SDRAM is susceptible to single event functional interrupts (SEFIs), the design team used byte-wide aspect ratio memories with individual power control for recovery. This paper will discuss the performance, power consumption, and status of this design.","PeriodicalId":114560,"journal":{"name":"2020 IEEE Aerospace Conference","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122799105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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