Orbit Determination from Two Line Element Sets of ISS-Deployed CubeSats

Deploying nanosatellites from the International Space Station (ISS) has become prevalent since the addition of the Nano Racks CubeSat Deployer in early 2014. Since then, 61 CubeSats have been deployed from the ISS, with the majority coming from the Planet Labs Flock 1 and Flock 1B constellations. CubeSats often rely on two-line elements (TLEs) made publicly available by the Joint Space Operations Center (JSpOC) for orbit determination and conjunction assessments, so the accuracy of JSpOC TLEs for ISS-deployed CubeSats is important to examine. In this work, the accuracy of TLEs of Flock 1B satellites are analyzed by comparison to orbits as derived from two way ranging. Ten Flock 1B satellites are examined for the month of September 2014, using 634 TLEs from start date to end date across the flock. Prior TLE assessments for CubeSats in LEO have estimated error to be within 1km. We found that error for ISS-deployed CubeSats is substantially higher than prior estimates. Using only forward propagation with the most recent TLE, as is the case for operational TLE use, median error in position is found to be4.52 km with a first quartile of 2.01 km and a third quartile of 10.6 km. The 1-σ in-track propagation error after one day ranges from 10-30 km among the 10 satellites, and the two-day 1-σ error ranges from 20-70 km. To improve TLE accuracy for on-orbit operations, a batch least squares estimation technique is used to estimate some or all elements of the current TLE based on prior TLEs. It is shown that this method can improve the propagation of a TLE significantly, particularly in cases of sparse updates, with up to 95% error reduction. This can potentially enable operations in cases where they would otherwise be lost due to inaccurate orbital knowledge

Design of a Free-Space Optical Communication Module for Small Satellites

Free-space optical (FSO) communication technology has the potential to provide power-efficient communication links for small satellites that outperform traditional radio frequency approaches. Extremely high-gain apertures at optical carrier frequencies enable significantly improved performance. We present a design for a miniaturized CubeSat-scale optical transmitter capable of supporting downlink rates up to at least 10 Mbps. Our design incorporates a fine-steering mechanism that augments the capabilities of the host spacecraft’s attitude determination and control system. In this work, we develop an optical layout that optimizes link performance metrics while staying within the size, weight, and power constraints of a payload within a standard 3U CubeSat. The selection criteria for critical components (detectors, optical sources, and steering mechanisms) are described. Simulation results showing sufficient beacon tracking performance (better than _210 μrad 3-s) are presented. Finally, single-axis simulation results are shown for the staged pointing control system that show the benefits of the fine stage

Development of a pointing, acquisition, and tracking system for a CubeSat optical communication module

Miniaturized satellites such as CubeSats continue to improve their capabilities to enable missions that can produce significant amounts of data. For most CubeSat missions, data must be downlinked during short low-earth orbit ground station passes, a task currently performed using traditional radio systems. Free-space optical communications take advantage of the high gain of a narrow optical beam to achieve better link efficiency, allowing more valuable data to be downlinked over the mission lifetime. We present the Nanosatellite Optical Downlink Experiment (NODE) design, capable of providing a typical 3U (30 x 10 x 10 cm) CubeSat with a comparatively high data-rate downlink. The NODE optical communication module is designed to fit within a 5 x 10 x 10 cm volume, weigh less than 1 kg, and consume no more than 10Wof power during active communication periods. Our design incorporates a fine-steering mechanism and beacon-tracking system to achieve a 10 Mbps link rate. We describe the system-level requirements and designs for key components, including a transmitter, a beacon tracking camera, and a fast-steering mirror. We present simulation results of the uplink beacon tracking and fine steering of the downlink beam, including the effects of atmospheric fading and on-orbit environmental disturbances to demonstrate the feasibility of this approach. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Integration and Testing of the Nanosatellite Optical Downlink Experiment

CubeSat sensor performance continues to improve despite the limited size, weight, and power (SWaP) available on the platform. Missions are evolving into sensor constellations, demanding power-efficient high rate data downlink to compact and cost-effective ground terminals. SWaP constraints onboard nanosatellites limit the ability to accommodate large high gain antennas or higher power radio systems along with high duty cycle sensors. With the growing numbers of satellites in upcoming scientific, defense, and commercial constellations, it is difficult to place the high-gain burden solely on the ground stations, given the cost to acquire, maintain, and continuously operate facilities with dish diameters from 5 meters to 20 meters. In addition to the space and ground terminal hardware challenges, it is also increasingly difficult and sometimes not possible to obtain radio frequency licenses for CubeSats that require significant bandwidth. Free space optical communications (lasercom) can cost-effectively support data rates higher than 10 Mbps for similar space terminal SWaP as current RF solutions and with more compact ground terminals by leveraging components available for terrestrial fiber optic communication systems, and by using commercial amateur-astronomy telescopes as ground stations. We present results from the flight unit development, integration, and test of the Nanosatellite Optical Downlink Experiment (NODE) space terminal and ground station, scheduled for completion by summer of 2017. NODE’s objective is to demonstrate an end-to-end solution based on commercial telecommunications components and amateur telescope hardware that can initially compete with RF solutions at \u3e10 Mbps and ultimately scale to Gbps. The 1550 nm NODE transmitter is designed to accommodate platform pointing errors \u3c 3 degrees. The system uses an uplink beacon from the ground station and an onboard MEMS fine steering mirror to precisely point the 0.12 degree (2.1 mrad) 200 mW transmit laser beam toward the ground telescope. We plan to downlink to an estalblished ground terminal at the Jet Propulsion Laboratory (JPL) Optical Communications Telescope Laboratory (OCTL) ground station as well as the new low-cost 30 cm amateur telescope ground station design to reduce overall mission risk. Moving beyond our initial laboratory prototyping captured in Clements et al. 2016 we discuss recent progress developing and testing the flight electronics, opto-mechanical structures, and controls algorithms, including demonstration of a hardware-in-the-loop test of the fine pointing system, for both the space and ground terminals. We present results of over-the-air testing of the NODE system, as we advance from benchtop to hallway to rooftop demonstrations. We will present thermal and environmental test plans and discuss experimental as well as expected results

NASA’s Terabyte Infrared Delivery (TBIRD) Program: Large-Volume Data Transfer from LEO

Satellites in low-Earth orbit (LEO) have on-board sensors that can generate large amounts of data to be delivered to a ground user. Direct-to-Earth delivery from LEO is challenging because of the sparse contact with a ground terminal, but the short link distances involved can enable very high data rates by exploiting the abundance of spectrum available at optical frequencies. We provide an overview and update of NASA’s Terabyte Infrared Delivery (TBIRD) program, which will demonstrate a direct-to-Earth laser communication link from a small satellite platform to a small ground terminal at burst rates up to 200Gbps. Such a link is capable of transferring several terabytes per day to a single ground terminal. The high burst rates are achieved by leveraging off-the-shelf fiber-telecommunications transceivers for use in space applications. A 2U TBIRD payload is currently being developed for flight on a 6U NASA CubeSat

Operations and Results from the 200 Gbps TBIRD Laser Communication Mission

Since launch in May 2022, the TeraByte Infrared Delivery (TBIRD) mission has successfully demonstrated 200 Gbps laser communications from a 6U CubeSat and has transferred up to 4.8 terabytes (TB) in a pass from low Earth orbit to ground. To our knowledge, this is the fastest downlink ever achieved from space. To support the narrow downlink beam required for high rate communications, the payload provides pointing feedback to the host spacecraft to precisely track the ground station throughout the 5-minute pass. The space and ground terminals utilize fiber-coupled coherent transceivers in conjunction with an automatic repeat request (ARQ) system to guarantee error-free communication through an atmospheric fading channel. This paper presents an overview of the link operations and mission results to date, as well as implications for future missions with high rate lasercom

Nanosatellite optical downlink experiment: design, simulation, and prototyping

The nanosatellite optical downlink experiment (NODE) implements a free-space optical communications (lasercom) capability on a CubeSat platform that can support low earth orbit (LEO) to ground downlink rates>10  Mbps. A primary goal of NODE is to leverage commercially available technologies to provide a scalable and cost-effective alternative to radio-frequency-based communications. The NODE transmitter uses a 200-mW 1550-nm master-oscillator power-amplifier design using power-efficient M-ary pulse position modulation. To facilitate pointing the 0.12-deg downlink beam, NODE augments spacecraft body pointing with a microelectromechanical fast steering mirror (FSM) and uses an 850-nm uplink beacon to an onboard CCD camera. The 30-cm aperture ground telescope uses an infrared camera and FSM for tracking to an avalanche photodiode detector-based receiver. Here, we describe our approach to transition prototype transmitter and receiver designs to a full end-to-end CubeSat-scale system. This includes link budget refinement, drive electronics miniaturization, packaging reduction, improvements to pointing and attitude estimation, implementation of modulation, coding, and interleaving, and ground station receiver design. We capture trades and technology development needs and outline plans for integrated system ground testing.United States. National Aeronautics and Space Administration. Research Fellowship ProgramLincoln Laboratory (Lincoln Scholars)Lincoln Laboratory (Military Fellowship Program)Fundación Obra Social de La Caixa (Fellowship)Samsung FellowshipUnited States. Air Force (Assistant Secretary of Defense for Research & Engineering. Contract FAs872105C0002

Aerodynamic Design for a 3-D Printable Mars Surface Lander

Printed electronics are expanding as a commercial industry and have great potential to advance space mission architecture. An end-to-end printed spacecraft has been proposed by a team at the NASA Jet Propulsion Laboratory, and a potential area that would greatly benefit from printed spacecraft are network missions. A proposed mission concept is to release a large number of these printed spacecraft on Mars and have them passively land to do basic sensing. In this work, we examine potential passive surface landers to fulfill this goal. The research presented here includes a survey of passive lander designs and an indepth analysis of an autorotator, a hexagonal pyramid, and a glider. Prototypes were designed, constructed, and tested experimentally for dispersion and ight stability. Monte Carlo simulations were developed for these vehicles in the Mars environment, allowing an estimate of dispersion. Finally, a basic subsystem layout was developed and some aspects of the communications and power subsystems for the spacecraft were addressed. Ultimately, the hexagonal pyramid and glider are recommended as potential surface lander designs. The hexagonal pyramid design had excellent stability and packing efficiency. However, the dispersion was estimated to only be on the order of tens of thousands of square meters. The glider design had a predicted dispersion on the order of tens of square kilometers, but suffered from potential stability issues in the Mars environment. While the ideal platform depends on specific mission requirements, through this work we develop insights and tools to characterize surface lander performance that can be used in more advanced planning stages

Portable optical ground stations for satellite communication

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 113-125).Small satellite technical capabilities continue to grow and launch opportunities are rapidly expanding. Several commercial constellations of small satellites for Earth observation and communications are making their way onto orbit, increasing the need for high bandwidth data downlink. Laser communications (lasercom) has the potential to achieve high data rates with a reduction in power and size compared to radio frequency (RF) communications, while simultaneously avoiding the significant regulatory burden of RF spectrum allocation. Lasercom benefits from high carrier frequencies and narrow beamwidths, but the resulting challenge is to precisely point these beams between transmit and receive terminals. Arcsecond to sub-arcsecond pointing is required from both the space terminal and the ground station. While existing lasercom ground stations have primarily utilized professional telescopes at observatory-class facilities, making optical ground stations more affordable and transportable is a key enabler for expanding lasercom to small satellites and new applications, as well as establishing networks to mitigate the effects of weather. We describe the development of the Massachusetts Institute of Technology Portable Telescope for Lasercom (MIT-PorTeL) utilizing an amateur telescope augmented with an externally mounted receiver assembly. The ground station has a 28 cm aperture and utilizes a star tracker for automated calibration. The ground station reduces mass by at least 10x and cost by at least 100 x over existing optical ground stations. We present a ground station architecture that enables deployment in less than one hour and that is capable of tracking satellites in low-Earth orbit. We describe the receiver assembly and fine pointing system that enables arcseconds-level pointing accuracy. Finally, we present results from testing the ground station on the roof of an MIT building tracking a star and tracking the International Space Station.by Kathleen Michelle Riesing.Ph. D

Development of a pointing, acquisition, and tracking system for a nanosatellite laser communications module

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 121-127).Launch opportunities for small satellites are rapidly growing and their technical capabilities are improving. Several commercial constellations of small satellites for Earth imaging and scientific observation are making their way onto orbit, increasing the need for high bandwidth data downlink. Obtaining regulatory licensing for current radio frequency (RF) communications systems is difficult, and state of the art nanosatellite RF systems struggle to keep up with the higher demand. Laser communications (lasercom) has the potential to achieve high bandwidth with a reduction in power and size compared to RF, while simultaneously avoiding the significant regulatory burden of RF spectrum allocation. Due to narrow beamwidths, the primary challenge of lasercom is the high-precision pointing required to align the transmitter and receiver. While lasercom has been successfully demonstrated on multiple spacecraft platforms, it has not yet been demonstrated on a scale small enough to meet the size, weight, and power constraints for nanosatellites. The Nanosatellite Optical Downlink Experiment (NODE) developed at MIT is designed to achieve a lasercom downlink of 10 to 100 Mbps within the constraints of a typical 3-U CubeSat. This thesis focuses on the development of the pointing, acquisition, and tracking system for NODE. The key to achieving a high bandwidth downlink is to bridge the gap between existing CubeSat attitude determination and control capabilities and the narrow beamwidths of lasercom. We present a two-stage pointing control system to achieve this. An uplink beacon and detector provide fine attitude feedback to enable precision pointing, and CubeSat body pointing is augmented with a fine steering mechanism. The architecture of the pointing, acquisition, and tracking system is presented, followed by the in-depth design and hardware selection. A detailed simulation of the ground tracking performance is developed, including novel on-orbit calibration algorithms to eliminate misalignment between the transmitter and receiver. A testbed is developed to characterize the selected fine steering mechanism for performance and thermal stability. The proposed system is capable of achieving at least two orders of magnitude better pointing than existing CubeSats to enable high bandwidth nanosatellite downlinks.by Kathleen Michelle Riesing.S.M