On July 14, 2015, the New Horizons mission accomplished the first flyby of Pluto-Charon, achieving full mission success during its primary mission. Less than 4 years later, during its first extended mission, New Horizons flew by Arrokoth, a 36-km contact binary trans-Neptunian object in the Kuiper Belt, on January 1, 2019. Along the way, New Horizons imaged numerous distant Kuiper Belt objects, performed important heliophysics science including complex Lyman-alpha radiation scans, and measured the dust and zodiacal light from regions never before explored. This article provides an overview of the New Horizons spacecraft and its engineering performance, as well as potential strategies for extending the mission far beyond its original design lifetime. Details on the mass and power budgets, as well as descriptions of key innovations to meet the challenges posed by the mission, offer insight into the engineering accomplishments that led to mission success. Trended data on the power, thermal, and propulsion systems substantiate projections of the mission's potential to continue its exploration beyond the heliopause until similar to 2050.

Very-long baseline interferometry (VLBI) allows for exceptionally high-resolution imaging in radio astronomy. Ultimately the angular resolution of radio interferometers and telescopes is determined by the separation between antennas in the array. Building on this fundamental concept, potential uses of existing spacecraft radio systems for VLBI are explored. Coherent observations performed between ground radio telescopes (GRT) and spacecraft require stringent drift tolerances for timing and synchronization between the GRT and spacecraft. Observed data using the spacecraft antenna is then recorded and stored on-board before downlink. Among candidate spacecraft, a promising contender and focus of this paper is New Horizons. Currently at a distance greater than 45 AU, New Horizons offers an outstanding baseline for astronomical radio observation and provides necessary, configurable instrumentation for performing an extended baseline observation in conjunction with a GRT or other spacecraft. Communications with New Horizons are synchronized with a 30 MHz clock signal using an ultra-stable oscillator (USO), providing an exceptional Allan Deviation of 3×10 -13 per one second integration time. Of the instruments on-board New Horizons, the Radio Science Experiment (REX) is of particular interest for its potential towards VLBI application. Developed for atmospheric measurements during occultations between the 7.182 GHz uplink from the 70 meter NASA Deep Space Network (DSN) antenna and Pluto/Charon, REX also successfully performed axial radiometric measurements of the Cygnus-A and Cassiopeia-A galaxies using the New Horizons high-gain antenna (HGA). The REX instrument's infusion with the New Horizons HGA allows for any radio measurement to be recorded, stored on-board, and ultimately to be downlinked to the DSN. For VLBI, New Horizons could receive command data for timed three-dimensional alignment synchronous to a ground-based observation. The observed data would then be recorded, downlinked, correlated, and processed for synthesized imaging. Using New Horizons for VLBI would be a proof-of-concept. With a fixed observation frequency, narrow bandwidth and receiver sensitivity of -177 dBm, New Horizons is limited as an extension for long-baseline radio interferometry. Given these restrictions, a successful VLBI measurement using New Horizons would still result in the highest angular resolution for any radio observation ever, at an astonishing 1.34 nanoarcseconds. Expanding the applications of New Horizons to VLBI observations encourages collaboration within the growing infrastructure for space-based astronomy.

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU69's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

Since the encounter with the Pluto system in 2015, the New Horizons team had been preparing for a flyby of the Kuiper Belt Object 2014MU69 (Ultima Thule). This paper discusses how the team designed and executed the flyby encounter within the various constraints imposed after the Pluto flyby. In addition to a brief overview of key spacecraft subsystems, this paper describes how the design needed to accommodate for large uncertainties in the target's position while minimizing image smear during science observations. The resource management, maneuver planning, and power and data downlink constraint management details are also explained.

The New Horizons spacecraft flew by Pluto on July 14, 2015, completing the first close up encounter of the Pluto system. The nine-day core command sequence surrounding closest approach was packed with 371 pointed maneuvers supporting observations and consumed approximately 6 kg of propellant. Inflight attitude data has been used to assess the performance of the guidance & control and propulsion systems and compare the results to pre-encounter estimates and simulations. In addition to the 9 days around closest approach, the spacecraft conducted science-pointing activities formally beginning on January 15, 2015 and concluded on July 30, 2015. To assure that the spacecraft had adequate resources to support all of the science requirements, a detailed budget of thruster cycles (open/close of each thruster) and propellant used was developed years in advance. Each maneuver and event was modeled and eventually simulated using assumptions and historic performance. This paper will present the various phases in the budgeting process, how the models and high fidelity simulations were validated, and how the real encounter numbers compared with the budgets. This paper will also document two different methods employed for tracking propellant usage, and how the type of maneuvers and events influenced the relationship between the two methods.

The temporal variability, or phenology, of animals and plants in coastal zone and marine habitats is a function of geography and climatic conditions, of the chemical and physical characteristics of each particular habitat, and of interactions between these organisms. These conditions play an important role in defining the diversity of life. The quantitative study of phenology is required to protect and make wise use of wetland and other coastal resources. We describe a low cost space-borne sensor and mission concept that will enable such studies using high quality, broad band hyperspectral observations of a wide range of habitats at Landsat-class spatial resolution and with a 3 day or better revisit rate, providing high signal to noise observations for aquatic scenes and consistent view geometry for wetland and terrestrial vegetation scenes.

The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition, its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.

The New Horizons spacecraft was launched on 19 January 2006. The spacecraft was designed to provide a platform for seven instruments designated by the science team to collect and return data from Pluto in 2015. The design meets the requirements established by the National Aeronautics and Space Administration (NASA) Announcement of Opportunity AO-OSS-01. The design drew on heritage from previous missions developed at The Johns Hopkins University Applied Physics Laboratory (APL) and other missions such as Ulysses. The trajectory design imposed constraints on mass and structural strength to meet the high launch acceleration consistent with meeting the AO requirement of returning data prior to the year 2020. The spacecraft subsystems were designed to meet tight resource allocations (mass and power) yet provide the necessary control and data handling finesse to support data collection and return when the one-way light time during the Pluto fly-by is 4.5 hours. Missions to the outer regions of the solar system (where the solar irradiance is 1/1000 of the level near the Earth) require a radioisotope thermoelectric generator (RTG) to supply electrical power. One RTG was available for use by New Horizons. To accommodate this constraint, the spacecraft electronics were designed to operate on approximately 200 W. The travel time to Pluto put additional demands on system reliability. Only after a flight time of approximately 10 years would the desired data be collected and returned to Earth. This represents the longest flight duration prior to the return of primary science data for any mission by NASA. The spacecraft system architecture provides sufficient redundancy to meet this requirement with a probability of mission success of greater than 0.85. The spacecraft is now on its way to Pluto, with an arrival date of 14 July 2015. Initial in-flight tests have verified that the spacecraft will meet the design requirements.

The NASA new horizons mission to the Pluto system and the Kuiper belt launched from Cape Canaveral on January 19, 2006 after a four-year development, and will arrive at Pluto closest-approach on July 14, 2015 after a 9.5- year cruise from Earth. Powered by a single radioisotope thermoelectric generator (RTG) from the Galileo-Cassini design and launched on the first flight of a Lockheed Martin Atlas V-551 with a Boeing STAR 48B third stage, the project overcame numerous technical and programmatic challenges to take advantage of the best-last opportunity using existing technology to perform the first-ever reconnaissance of the Pluto system in our lifetime. The mission design for the 2006 launch uses a Jupiter gravity assist to achieve the shortest possible flight time. A rich science return from the Jupiter flyby (February 28, 2007) has been achieved. The engineering and programmatic challenges associated with the spacecraft design, RTG procurement, integration of Lockheed Martin and Boeing launch vehicle components, and the launch approval process are discussed. The current status of the spacecraft and mission is presented.

On January 19, 2006, the Pluto-New Horizons spacecraft was launched from Cape Canaveral Air Force Station (CCAFS) with a radioisotope thermoelectric generator (RTG) as the power source and a 30V power regulation and distribution system designed and built by the Johns Hopkins University Applied Physics Laboratory. Pluto-New Horizons is the flagship spacecraft of NASA’s New Frontiers program of medium-class interplanetary missions and targets the first reconnaissance of Pluto and its moon, Charon, and the Kuiper Belt. Arrival at Pluto is scheduled for July, 2015 at which time the spacecraft will have traveled 3 billion miles and be almost 32 AU from the sun. Due to the extended mission duration and extreme distance from the sun, a RTG was chosen as the spacecraft’s power source. RTG missions place complexity on the spacecraft power system design due to their unique power characteristics and limited opportunities for test prior to pre-launch field operations. The RTG integration and test with the spacecraft results are presented along with the spacecraft power system performance during launch and in the early mission phase. These in-flight operational results demonstrate a fully functioning power system that will supply the spacecraft with safe and reliable power during the exploration of the farthest reaches of the solar system.

Pluto is the only planet in our solar system that has not yet been visited by a spacecraft from Earth. Beyond the orbit of Pluto lies the Kuiper-Belt: home to many primordial objects from the earliest days of the formation of the solar system, preserved in a cosmic deep freeze. The Johns Hopkins University/Applied Physics Laboratory (JHU/APL) is planning the mission for the Principal Investigator, Dr. S. Alan Stern of Southwest Research Institute. The planned design of the New Horizons spacecraft, along with a discussion of the design drivers, is presented. The design lifetime of the spacecraft would be 15.25 years. Measures taken to ensure the reliable operation of the spacecraft over the life of the planned mission are discussed.

A multispectral imager has been developed for a rendezvous mission with the near-Earth asteroid, 433 Eros. The Multi-Spectral Imager (MSI) on the Near-Earth Asteroid Rendezvous (NEAR) spacecraft uses a five-element refractive optical telescope, has a field of view of 2.93 × 2.25°, a focal length of 167.35 mm, and has a spatial resolution of 16.1 × 9.5 m at a range of 100 km. The spectral sensitivity of the instrument spans visible to near infrared wavelengths, and was designed to provide insight into the nature and fundamental properties of asteroids and comets. Seven narrow band spectral filters were chosen to provide multicolor imaging and to make comparative studies with previous observations of S asteroids and measurements of the characteristic absorption in Fe minerals near 1 µm. An eighth filter with a much wider spectral passband will be used for optical navigation and for imaging faint objects, down to visual magnitude of +10.5. The camera has a fixed 1 Hz frame rate and the signal intensities are digitized to 12 bits. The detector, a Thomson-CSF TH7866A Charge-Coupled Device, permits electronic shuttering which effectively varies the dynamic range over an additional three orders of magnitude. Communication with the NEAR spacecraft occurs via a MIL-STD-1553 bus interface, and a high speed serial interface permits rapid transmission of images to the spacecraft solid state recorder. Onboard image processing consists of a multi-tiered data compression scheme. The instrument was extensively tested and calibrated prior to launch; some inflight calibrations have already been completed. This paper presents a detailed overview of the Multi-Spectral Imager and its objectives, design, construction, testing and calibration.

The Applied Physics Laboratory has developed a general-purpose spacecraft computer suitable for many subsystem applications on the Midcourse Space Experiment (MSX) spacecraft. This article presents the major features of the computer and common interface boards and describes three MSX subsystems that use them.

The amount of electronics involved in the Midcourse Space Experiment (MSX) required that common designs be used wherever possible. Three instruments—the tracking processor, the attitude processor, and the Ultraviolet and Visible Imagers and Spectrographic Imagers (UVISI) image processor—each use a general-purpose computer designed for MSX as well as common interface boards. Reference 1 describes the system requirements, design trade-offs, and computer features in great detail. Those features are summarized in what follows (see also Table 1).