The Cold Atom Lab (CAL) launched to the International Space Station (ISS) in May 2018 and has been entirely remotely operated from NASA's Jet Propulsion Laboratory since then as the world's first multi-user facility for studying ultra-cold atoms in space. CAL uses lasers and magnetic traps to cool atoms down to less than a degree above absolute zero. When clouds of atoms reach these ultracold temperatures, they form a fifth state of matter called a Bose-Einstein Condensate (BEC). Distinct from gasses, liquids, solids, and plasmas, a BEC makes the quantum properties of atoms macroscopic, so scientists can more easily observe and interact with them in the essentially limitless free-fall of ISS. An on-orbit upgrade to CAL in 2021 enabled the study of atom interferometry (AI) in space, which uses the interference of atomic matter waves as exquisitely precise sensors for fundamental forces, including gravity, accelerations, and rotations. Relevant to Earth and planetary sciences, these quantum sensors are expected to serve as precision gravity sensors for geodesy, seismology, and subsurface mapping in the near future. We will discuss our efforts to provide pioneering, microgravity-enabled quantum gas research capabilities with CAL, to demonstrate AI for the first time in Earth's orbit, to realize simultaneous, dual-species atom interferometry in space, and to mature this technology for future mission opportunities. © 2024 California Institute of Technology. Government sponsorship acknowledged.

Deployment of ultracold atom interferometers (AI) into space will capitalize on quantum advantages and the extended freefall of persistent microgravity to provide high-precision measurement capabilities for gravitational, Earth, and planetary sciences, and to enable searches for subtle forces signifying physics beyond General Relativity and the Standard Model. NASA’s Cold Atom Lab (CAL) operates onboard the International Space Station as a multi-user facility for fundamental studies of ultracold atoms and to mature space-based quantum technologies. We report on pathfinding experiments utilizing ultracold 87Rb atoms in the CAL AI. A three-pulse Mach–Zehnder interferometer was studied to understand the influence of ISS vibrations. Additionally, Ramsey shear-wave interferometry was used to manifest interference patterns in a single run that were observable for over 150 ms free-expansion time. Finally, the CAL AI was used to remotely measure the Bragg laser photon recoil as a demonstration of the first quantum sensor using matter-wave interferometry in space. NASA’s Cold Atom Lab has operated on the International Space Station since 2018 to study quantum gases and mature quantum technologies in Earth’s orbit. Here, Williams et al., report on a series of pathfinding experiments exploring the first quantum sensor using atom interferometry in space.

Ultracold atomic gases hold unique promise for space science by capitalizing on quantum advantages and extended freefall, afforded in a microgravity environment, to enable next-generation precision sensors. Atom interferometers are a class of quantum sensors which can use freely falling gases of atoms cooled to sub-photon-recoil temperatures to provide unprecedented sensitivities to accelerations, rotations, and gravitational forces, and are currently being developed for space-based applications in gravitational, earth, and planetary sciences, as well as to search for subtle forces that could signify physics beyond General Relativity and the Standard Model. NASA's Cold Atom Lab (CAL) operates onboard the International Space Station as a multi-user facility for studies of ultracold atoms and to mature quantum technologies, including atom interferometry, in persistent microgravity. In this paper, we report on path-finding experiments utilizing ultracold $^{87}$Rb atoms in the CAL atom interferometer, which was enabled by an on-orbit upgrade of the CAL science module: A three-pulse Mach-Zehnder interferometer was studied to understand limitations from the influence of ISS vibrations. Additionally, Ramsey shear-wave interferometry was used to manifest interference patterns in a single run that were observable for over 150 ms free-expansion time. Finally, the CAL atom interferometer was used to remotely measure the photon recoil from the atom interferometer laser as a demonstration of the first quantum sensor using matter-wave interferometry in space.

NASA’s Cold Atom Laboratory (CAL) is a multi-user science facility for studying quantum gases in the microgravity environment of the International Space Station. The persistent microgravity environment of the ISS enables research with ultracold atoms in a temperature regime and force-free environment inaccessible to terrestrial laboratories, unlocking the potential to observe novel quantum phenomena. CAL launched to the ISS in May 2018, and has operated continuously since then as the world’s first multi-user quantum science facility in space. CAL is the first experimental facility to produce the fifth state of matter known as a Bose-Einstein condensate with ultracold rubidium atoms on orbit [1] and, more recently, with mixtures of rubidium and potassium [2]. We present an overview of CAL’s design and operation, review the scientific contributions to date, and discuss recent on-orbit upgrades to extend its useful mission lifetime and provide enhanced science. We also consider opportunities for follow-on missions informed by lessons learned from over five years of operation on orbit.

The capability to reach ultracold atomic temperatures in compact instruments has recently been extended into space. Ultracold temperatures amplify quantum effects, while free-fall allows further cooling and longer interactions time with gravity - the final force without a quantum description. On Earth, these devices have produced macroscopic quantum phenomena such as Bose-Einstein condensation (BECs), superfluidity, and strongly interacting quantum gases. Quantum sensors interfering the superposition of two ultracold atomic isotopes have tested the Universality of Free Fall (UFF), a core tenet of Einstein's classical gravitational theory, at the 10^-12 level. In space, cooling the elements needed to explore the rich physics of strong interactions and preparing the multiple species required for quantum tests of the UFF has remained elusive. Here, utilizing upgraded capabilities of the multi-user Cold Atom Lab (CAL) instrument within the International Space Station (ISS), we report the first simultaneous production of a dual species Bose-Einstein condensate in space (formed from ^87Rb and ^41K), observation of interspecies interactions, as well as the production of ^39K ultracold gases. We have further achieved the first space-borne demonstration of simultaneous atom interferometry with two atomic species (^87Rb and ^41K). These results are an important step towards quantum tests of UFF in space, and will allow scientists to investigate aspects of few-body physics, quantum chemistry, and fundamental physics in novel regimes without the perturbing asymmetry of gravity.

On February 18, 2021, NASA's Mars 2020 Rover “Perseverance” conducted the Entry, Descent, and Landing (EDL) sequence to land safely on the surface of Mars at Jezero Crater. Due to the criticality of the EDL sequence, redundant telecommunications strategies were utilized to observe the event. The rover transmitted an X-band (8.4 GHz) signal encoded with Multiple Frequency Shift Keying tones direct-to-Earth and a UHF (401.5 MHz) signal with 8 kbps encoded telemetry to orbiters, which relayed the signal back to Earth at X-band. NASA's Deep Space Network complexes at Goldstone, California and Madrid, Spain received the direct-to-Earth X-band signal. Two of the largest steerable radio telescopes in the world, the 100-meter Green Bank Telescope in West Virginia and the Effelsberg 100-meter Radio Telescope in Germany also received the UHF carrier signal on Earth. During the EDL event, full spectrum recordings of the UHF and X-band signals were captured at these observatories using open-loop receivers. Real-time and post-processing signal analysis to determine power level, received frequency, and Doppler shift allowed determination of the spacecraft's health and safety state during critical sequences, including event detection such as atmospheric entry, plasma blackouts, and parachute deployment. Simultaneous observations of the UHF and X-band radio links allow for redundancy in the event of a fault and greatly improve confidence in Doppler event detection.

This paper discusses the analysis of the UHF (401 MHz) plasma-induced communications blackout (and brownout) experienced by the Mars InSight spacecraft during its entry, descent, and landing (EDL) phase into the Martian atmosphere on 26 November 2018. The UHF relay links from InSight to the Mars Reconnaissance Orbiter and to the Mars Cube One A and Mars Cube One B CubeSats suffered a period of about 52 s of degradation, consisting of a combination of brownout (signal fades) and blackout (complete loss of signal). The observed signal fades and outages on these proximity links spanned the interval from about 48 to 100 s after entry started at the atmospheric interface. In addition, the degradation of the weaker signal received at the Green Bank, West Virginia 100 m radio telescope is also discussed, which occurred from about 40 to 120 s after atmospheric entry. The observations were in agreement with existing models of signal degradation given the entry trajectory of the vehicle. This paper discusses model estimates and measurements of signal degradation during the peak heating phase of the InSight EDL, as well as the results of high-fidelity analysis performed using computational fluid dynamics tools.

Spacecraft-to-ground bistatic radar is an established technique that has enabled the study of the planetary surfaces and near sub-surfaces properties by using the telecommunication signals amplitude, phase, and polarization. The Planetary Radar and Radio Science group at the Jet Propulsion Laboratory (JPL) has been involved in many planetary bistatic radar experiments since the 1970's using orbiters and Deep Space Network (DSN) antennas. The recent advances in Unmanned Aerial Vehicles (UAVs) technologies are making the UAVs more popular in scientific surveying applications. One such application is the use of UAVs in bistatic radar measurements to explore surfaces on Earth. Our analyses show that UAV-based bistatic radar measurements will improve our understanding of the finer-scale characteristic variations of the surface by acquiring the higher resolution data for a specific region of interest compared to data obtained from a spacecraft. The Mars helicopter, a technology demonstration to test the first powered flight on Mars, will be the beginning of a new era of exploration with UAVs on Mars. This leap in planetary UAV technology has renewed the importance of developing a miniaturized bistatic radar instrument (under 1 kg) compatible with a UAV platform able to meet the science requirements for studying surfaces on Earth, Mars, and other planetary bodies. As part of a task at JPL, we have been working on a technology demonstration using a compact bistatic radar instrument designed to be the payload of a UAV employing signals of opportunity from Earth's orbiters, i.e. Global Positioning System (GPS). In this paper, we present our design and development of the instrument, our evaluation of different L-band antennas, the performance of compact open-loop receivers in support of Earth and planetary bistatic radar observations, and the instrument fit test on an UAV platform. As part of this publication, we also highlight the results of a field experiment dedicated to test the sensitivity of the miniaturized bistatic radar instrument to different electrical properties of the surface.

The Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) spacecraft landed successfully on 26 November 2018 to conduct an exploration of the interior of Mars. To meet NASA's requirement for communications during critical events, the InSight lander transmitted telemetry continuously throughout entry, descent, and landing. This allowed the public to witness the landing in real time. The transmissions were received by five assets: three at Mars and two on Earth. These included real-time relay of telemetry by the first deep-space CubeSats. This paper describes the constraints on the design of an entry, design, and landing communication link; the uncertainties in the trajectory; and the modeling that was used to meet these constraints. It then reports on the actual performance of each link, including an unexpected degradation of signal to the Mars Reconnaissance Orbiter. The lessons learned from this process contributed to the successful relay of data from the Perseverance lander, as well as to the design of future landing communications systems.

This article is the second of a three-part series in which we present the results of a study exploring concepts for improving communications and tracking capabilities of deep space SmallSats. In Part I, we discussed SmallSat direct-to-earth links and SmallSat communications equipment, and provided recommendations for future work. In Part II, we focus on SmallSat navigation options, Disruption Tolerant Networking (DTN), proximity links, and the use of the communication link for science observations, and we provide recommendations for future work. We have examined both radio and optical navigation options, and considered autonomous and semiautonomous navigation to reduce operational costs for planetary SmallSats. We note that communication link resilience to delay and disruption enhances spacecraft autonomy; therefore, we have provided a discussion of DTN to indicate that using DTN allows for automated data transmission and recovery, therefore, reducing manual operations. SmallSats in deep space may utilize a relay spacecraft for communications with earth or function as a relay for landed and in-orbit assets. We present a detailed examination of relay proximity links and networks where we address both proximity hardware and networking scenarios. The proximity link features that we examine include the network architecture and its relationship to DTN, proximity radios and antennas, communications link performance, and proximity navigation. The use of the communication link for science has been practiced by primary missions in deep space scenarios. (Two examples of past planetary radio science experiments can be found in the following: https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/radio-science-subsystem/ and https://www.boulder.swri.edu/pkb/ssr/ssr-rex.pdf) Likewise, SmallSats can offer their radio links for radio science investigations. This article provides a brief introduction to radio science and presents the prerequisite features necessary for radio science observations by SmallSats. We conclude with nine recommendations based on the findings of the study. These recommendations are guidelines on the design, implementation, and operation of deep space SmallSat communication links. The adoption of some or all of the guidelines should result in an enhanced communication and tracking capability for the deep space SmallSat missions.

This paper discusses recent activities at JPL that are focused on extending the Opportunistic Multiple Spacecraft Per Antenna (OMSPA) concept to include arraying multiple antennas. Specifically, we explore the ability to process multiple open loop recordings associated with multiple antennas and perform the appropriate alignment and combining. We focus on using the symbol stream combining technique and provide examples of performance measurements on actual spacecraft signals for MarCO A and B as well as the Mars Express.

Smallsats and cubesats have been suggested as low-cost alternative means to achieve scientific goals for interplanetary missions. On May 5, 2018, NASA launched the first interplanetary cubesat: Mars Cube One (MarCO). MarCO-A and MarCO-B are twin communications-relay cubesats designed to monitor InSight during its Entry, Descent and Landing (EDL) on November 26, 2018. After InSight's EDL, MarCO continued to flyby Mars and conduct a radio occultation of the planet. This is the first-ever radio occultation of a planet other than Earth performed, and also the first planetary science measurement taken by an interplanetary cubesat. This research presents a performance assessment of the MarCO radio science measurements, results of MarCO radio occultation task, and the expected radio science capability of MarCO-like cubesat. Future interplanetary radio science missions can investigate planetary atmospheres, ionospheres, and rings using radio occultation measurements; probe the interior of a planetary body with gravity measurements; and surface characteristics with bistatic scattering. Observations made by tracking MarCO from NASA's Deep Space Network using an open-loop recordings of the X-band radio signal collected during cruise, InSight EDL, and the MarCO radio occultation are presented. Although the noise level of the MarCO radio occultation was too high for precise remote sensing of the atmosphere, the noise patterns are presented and analyzed against simulations. We compared observations with the spacecraft dynamics, Earth atmospheric and ionospheric calibrations, Martian atmospheric and ionospheric model simulations to evaluate the performance of the MarCO radio occultation. This investigation will improve our understanding of engineering and science constraints for future interplanetary cubesats.

Robotic exploration of the solar system using small satellites (SmallSats) is gaining popularity because of SmallSats' lower cost and faster development cycle compared to primary science missions. A potential obstacle for deployment of SmallSats in deep space is the limitation associated with the communications link imposed by SmallSats' frugal power and antenna size. These technical limitations constrain the range and throughput of SmallSats and may impact their navigation performance. To allow SmallSats to play a greater role in deep space science endeavors, we propose an enhanced communications architecture that will lessen the communications disparity between larger, more expensive missions and SmallSats. The objectives of the study are to define a communications architecture, in-flight and flight-to-ground, that is needed for planetary SmallSats, both standalone or in support of a larger mission; and to develop a guideline for primary spacecraft that would communicate with ride-along SmallSats. This work treats the space segment and the ground network as a whole to provide for improvements not only via investments in technology, but also via improvements in operational procedures. The study includes reviews of current communication concepts, technologies, and procedures, as well as an assessment of navigation needs, evaluation of the communication architecture performance for a range of destinations and applications, and identification of any gaps in capability. The study product is a set of recommendations to space agencies and the planetary SmallSat community. The main thrust of these recommendations is investment in technology, such as radios, antennas, protocols, and methodologies. The concepts for improving communications capability of deep space SmallSats are discussed in a series of three articles, Improving Small Satellite Communications in Deep Space. In this article, Part I, we discuss SmallSat direct-to-Earth links, as well as SmallSat communications equipment. In Part II, we discuss navigation topics, proximity links and networks, and the use of the communications channel for science observations. We present the ground network in Part III. Definitions and assumptions are provided here in Part I.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Wireless technologies have been widely applied in many communication systems on Earth to enhance the transmission data rate, improve the receiving signal-to-noise-ratio (SNR), and increase the channel capacity. For flight mission and spacecraft design, reliable wireless systems will expand the scientific applications and research opportunities of planetary explorations. To retire key risks to use of wireless technologies in spacecraft design and space applications, in this research, we analyze its capability and propagation in the test and operational environments including thermal chamber and on-board of a rover at JPL Mars yard. The software-based wireless system consists a transmitting antenna, two receiving antennas, and a software defined radio, which enable one to transmit and receive multiple frequency band wireless signals with different modulations and a flexible data rate. Here, we summarize the signal propagation analysis of different test and operational scenarios. The propagation analysis demonstrates that the design of two receiving antennas provides about 20 dB improvement in the received power comparing to the single-antenna result. Additionally, the chamber test result shows significant multipath effects observed from the data collected from the two scenarios: 1) transmitting and receiving antennas are inside of the chamber, and 2) the inside-chamber receiving antennas receive signals from the outside-chamber transmitter. The statistical analysis of the Mars yard test indicates that signal power has relatively small standard deviation for the scenario in which transmitting and receiving antennas are aligned in the line of sight directiaon with a distance. The standard deviations increase for other scenarios that transmitter is set on rover's wheel, and receiving antennas are on the top of the rover probably due to multi-path effects. The investigation of propagation analysis will be beneficial to a design of a reliable wireless system toward the development of the spacecraft wireless networks in support of NASA's future flight missions (such as planetary aerobots, rovers, and spacecraft).

This paper discusses recent activities at JPL that are focused on the development of wireless communications for data path connectivity between instruments and subsystems within the confines of a single spacecraft. Anticipated benefits of intra-spacecraft wireless links include reduction of cable mass, improved flexibility in spacecraft design or modifications and increased efficiencies during integration and test. This paper describes the framework for this effort, plans for retiring key risks and progress to date. Three of the primary risks addressed under this effort are communications link reliability, scalability and electromagnetic compatibility. In this paper, we will discuss analysis and test methods used to investigate each of these areas. In addition, we will describe a number of use cases for both operational and test applications that are under current investigation and development.

The goal of the Deep Space Optical Communications project at the Jet Propulsion Laboratory is to demonstrate laser communication links at ranges out to approximately 3 AU. In this paper, we discuss a downlink receiver concept capable of demodulating optical pulse-position modulated (PPM) waveforms with data rates varying from approximately 50 kbps up to 265 Mbps, using a range of PPM orders, slot widths, and code rates. The receiver operates on recorded timestamps corresponding to the times-of-arrival of photons detected by a photon-counting detector array followed by a commercial time-tagger. Algorithms are presented for slot, symbol, and frame synchronization as well as parameter estimation. Estimates of link performance are evaluated through Monte Carlo simulation for an optical channel that includes optical losses, detector blocking, signal clock dynamics, and pointing-induced downlink fades. Based upon these simulation results, it is expected that link closure may be achieved with at least 3 dB of margin under a variety of relevant conditions.

. — The Opportunistic Multiple Spacecraft Per Antenna (OMSPA) concept seeks to provide smallsat missions with a low-attributed-aperture-fee technique for obtaining rou-tine downlink in a manner that is very low cost to the Deep Space Network (DSN). Unlike traditional MSPA in which the number of spacecraft that can be supported is limited by the number of available receivers, OMSPA makes use of a digital recorder at each station that is capable of capturing IF signals from every spacecraft in the antenna beam within the frequency bands of interest. When smallsat missions see one or more opportunities to intercept the traditionally scheduled antenna beam of a “host” spacecraft, they can trans-mit open loop during those opportunities. Via a secure Internet site, the smallsat mission operators can then retrieve relevant portions of the digital recording for subsequent de-modulation and decoding or subscribe to a service that does it for them. The demonstra-tion discussed in this article was intended to provide prospective smallsat users and the DSN, as the prospective service provider, with demonstrable proof that the OMSPA concept is, in fact, an operationally viable means for obtaining routine downlink telemetry. To do this, the demonstration began by treating Mars Odyssey as a “smallsat” and Mars Recon-naissance Orbiter (MRO) as the “host” spacecraft. Using a specially created Beam Intercept Planning System (BIPS) and a DSN 7-Day Schedule Cross-Comparison (7-DSC) tool, oppor-tunities were identified when Mars Odyssey would be transmitting while in MRO’s ground antenna beam. Existing Very Long Baseline Interferometry (VLBI) Science Receivers (VSRs) were used to record the Mars Odyssey downlink telemetry during these opportunities. The recordings were played back to a secure server outside the Flight Operations Network firewall, but inside the JPL firewall. The demonstration team’s signal processing personnel retrieved the recordings from this secure server and downloaded them to a workstation con-taining an OMSPA Software Demodulator (OSD) tool that was developed to demodulate and decode the Mars Odyssey signal. Validation of the recovered data was then accomplished by comparing the transfer frames obtained through OMSPA with those recovered via Mars Odyssey’s formally scheduled downlink. The demonstration successfully achieved its