Near Earth Asteroid Rendezvous Spacecraft Research Articles

Using a Volume Discretization Method to Compute the Surface Gravity of Irregular Small Bodies

In the orbit design for small body exploration missions, it is important to take the effect of the gravitation of the small body into consideration. However, the majority of small bodies in the solar system are irregularly shaped with a non-uniform density distribution, this makes it difficult to precisely calculate the gravitational fields of these bodies. This paper proposes a method to model the gravitational field of an irregularly shaped small body, and calculate the corresponding spherical harmonic coefficients. This method is based on the shape of the small body resulted from the observed light curve, and uses finite volume elements to approximate the body shape. The spherical harmonic coefficients can be derived numerically by computing the integrals according to their definitions. A comparison is made with the polyhedron method. Taking the asteroid (433) Eros as an example, the spherical harmonic coefficients calculated by this method are compared with the result derived from the inversion of the NEAR (Near-Earth Asteroid Rendezvous) spacecraft’ orbit data, and the comparison shows that the error of C20 is less than 2%. Using this method, we have calculated the gravity field of (1996) FG3 which is a candidate target in our future space exploration mission. Taking (4179) Toutatis, the target body of the Chang’e 2's flyby mission, as an example, the distribution of surface gravitational potential is calculated, in combination with the shape model derived from the radar data, it provides a theoretical basis for analyzing the surface soil distribution and flow direction from the optical images obtained in this mission. This method suits the objects of inhomogeneous density distribution, and can be used to provide the reliable gravitational data of small bodies for the orbit design and landing in future asteroid exploration missions.

Near-IR Reflectance Spectroscopy of 433 Eros from the NIS Instrument on the NEAR Mission: I. Low Phase Angle Observations

From February 13 to May 13, 2000, the near-infrared spectrometer (NIS) instrument on the Near Earth Asteroid Rendezvous (NEAR) spacecraft obtained more than 200,000 spatially resolved 800- to 2500-nm reflectance spectra of the S-type asteroid 433 Eros. An important subset of the spectra was obtained during a unique opportunity on February 13 and 14, when the NEAR spacecraft flew directly through the 0° phase angle point between Eros and the Sun just prior to the orbital insertion maneuver. This low phase flyby (LPF) dataset consists of ∼2000 spectra of the northern hemisphere of Eros, obtained from 1° to 47° phase angle and at spatial resolutions of between 6×12 km to 1.25×2.50 km per spectrum. The spectra were calibrated to radiance factor (I/F, where I=observed radiance and πF=solar input radiance) and then photometrically corrected to normal albedo. The average northern hemisphere spectrum of Eros is similar to the asteroid's unresolved telescopic spectrum and exhibits absorption features near 1000 nm (Band I) and 2000 nm (Band II) consistent with an orthopyroxene to orthopyroxene+olivine (opx+ol) mixing ratio of approximately 0.38±0.08. The ensemble of NIS LPF spectra falls primarily within the S(IV) to upper S(III) fields of the Gaffey et al. (1993) S-asteroid classification scheme and exhibits Band I and Band II properties similar to those of ordinary chondrite meteorites. While some small spatially coherent spectral variations have been detected, neither the opx/opx+ol) mixing ratio nor other spectral parameters vary spatially by more than ∼1σ across the entire northern hemisphere of the asteroid, suggesting a remarkable homogeneity of the composition and mineralogy of the uppermost regolith. Spectral mixture modeling suggests that the presence of glass and/or a reddening agent like nanophase iron, likely formed from exposure of the regolith to the space environment, is a component of the surface of Eros. Reddening and darkening components could also explain the dissimilarity in overall spectral slope and albedo between Eros and other S(IV) asteroids and ordinary chondrite meteorites. The largest (but still weak) spectral variations across the surface are seen in the depths of Band I and Band II, which are greatest in and around the largest craters and at the 0° longitude “nose” of the asteroid, and in the Band II/Band I area ratio between the large impact craters Psyche and Himeros. These subtle NIS spectral variations are usually associated with albedo and surface slope variations seen in NEAR imaging and topographic data and appear to be related to downslope movement of regolith materials.

Determination of Shape, Gravity, and Rotational State of Asteroid 433 Eros

Prior to the Near Earth Asteroid Rendezvous (NEAR) mission, little was known about Eros except for its orbit, spin rate, and pole orientation, which could be determined from ground-based telescope observations. Radar bounce data provided a rough estimate of the shape of Eros. On December 23, 1998, after an engine misfire, the NEAR-Shoemaker spacecraft flew by Eros on a high-velocity trajectory that provided a brief glimpse of Eros and allowed for an estimate of the asteroid's pole, prime meridian, and mass. This new information, when combined with the ground-based observations, provided good a priori estimates for processing data in the orbit phase.After a one-year delay, NEAR orbit operations began when the spacecraft was successfully inserted into a 320×360 km orbit about Eros on February 14, 2000. Since that time, the NEAR spacecraft was in many different types of orbits where radiometric tracking data, optical images, and NEAR laser rangefinder (NLR) data allowed a determination of the shape, gravity, and rotational state of Eros. The NLR data, collected predominantly from the 50-km orbit, together with landmark tracking from the optical data, have been processed to determine a 24th degree and order shape model. Radiometric tracking data and optical landmark data were used in a separate orbit determination process. As part of this latter process, the spherical harmonic gravity field of Eros was primarily determined from the 10 days in the 35-km orbit. Estimates for the gravity field of Eros were made as high as degree and order 15, but the coefficients are determined relative to their uncertainty only up to degree and order 10. The differences between the measured gravity field and one determined from a constant density shape model are detected relative to their uncertainty only to degree and order 6. The offset between the center of figure and the center of mass is only about 30 m, indicating that Eros has a very uniform density (1% variation) on a large scale (35 km). Variations to degree and order 6 (about 6 km) may be partly explained by the existence of a 100-m, regolith or by small internal density variations. The best estimates for the J2000 right ascension and declination of the pole of Eros are α=11.3692±0.003° and δ=17.2273±0.006°. The rotation rate of Eros is 1639.38922±0.00015°/day, which gives a rotation period of 5.27025547 h. No wobble greater than 0.02° has been detected. Solar gravity gradient torques would introduce a wobble of at most 0.001°.

Calibration of Radiometric Data for Relativity and Solar Plasma During a Solar Conjunction

The round trip propagation time of a radio signal passing close to the Sun is affected by the charged particle environment of the solar plasma and the increased path length associated with the curvature of space predictedby general relativity. It has been difficult to separate estimates of the individual contributions to the signal delay. In January 1997, the Near Earth Asteroid Rendezvous (NEAR) spacecraft passed through a deep solar conjunction. For a month before and after conjunction, the spacecraft was pointed at the Sun and attitude operations were suspended. Since the NEAR spacecraft is equipped with two way X-band Doppler and range and the spacecraft attitude was favorable, a high precision spacecraft ephemeris was obtained. Data from the solar conjunction period of the NEAR mission is used to solve explicitly for the total electron content of the solar plasma along the signal path by using the signal delay in the range data to calibrate the signal advance in the Doppler data. The result is a precise estimate of the general relativity delay, and of the total electron content along the signal path, which can be used to improve models of the plasma emanating from the Sun. The general relativity parameter y is determined to less than 0.5 percent, which is competitive with the most accurate current verifications of general relativity.

A comparison of NEAR actual spacecraft costs with three parametric cost models

Costs for modern (post-1990) U.S.-built small planetary spacecraft have been shown to exhibit significantly different trends from those of larger spacecraft. These differences cannot be accounted for simply by the change in size alone. Some have attributed this departure to NASA's “faster, better, cheaper” design approach embodied by the efficiency of smaller teams, reduced government oversight, increased focus on cost, and short development periods. With the Discovery, Mars Surveyor and New Millennium programs representing the new approach to planetary exploration, it is important to understand these current cost trends and to be able to estimate costs of future proposed missions. To address this issue, The Aerospace Corporation (hereafter referred to as Aerospace) performed a study to compare the actual costs of the Near Earth Asteroid Rendezvous (NEAR) spacecraft bus (instruments were not estimated) using three different cost models; the U.S. Air Force Unmanned Spacecraft Cost Model, Version 7 (USCM-7), the Science Applications International Corporation (SAIC) NASA/Air Force Cost Model 1996 (NAFCOM96) and The Aerospace Corporation's Small Satellite Cost Model 1998 (SSCM98). The NEAR spacecraft was chosen for comparison because it was the first Discovery mission launched, and recently recognized with a Laurel award by Aviation Week and Space Technology as a benchmark for NASA's Discovery program [North, 1997]. It was also selected because the cost data has been released into the public domain [Hemmings, 1996]which makes it easy to discuss in a public forum. This paper summarizes the NEAR program, provides a short synopsis of each of the three cost models, and demonstrates how they were applied for this study.

Estimating the mass of asteroid 433 eros during the NEAR spacecraft flyby

The Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 3830 kilometers of asteroid 433 Eros on 23 December 1998. The gravitational perturbation on NEAR was evident in the spacecraft tracking data. Ground-based Doppler and range tracking of the spacecraft as well as spacecraft images of the asteroid's center of figure and surface features were used to determine the mass and rotation pole of Eros. The mass of Eros is (7.2 +/- 1.8) x 10(18) grams and, coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a bulk density of 2.5 +/- 0.8 grams per cubic centimeter. The rotation pole position is 15.6 (+/-3.7) degrees in right ascension and 16.4 (+/-1.8) degrees in declination, which is consistent with ground-based and NEAR imaging team observations.

Inflight Calibration of the NEAR Multispectral Imager

The multispectral imager on the Near-Earth Asteroid Rendezvous spacecraft has been subjected to a comprehensive series of inflight tests to validate its radiometric characteristics measured onground and to characterize instrument stability, pointing, geometric distortion, coalignment with other instruments, and light-scattering characteristics under flight conditions. The results of these tests, described herein, support the conversion of images of 253 Mathilde and 433 Eros into scientifically valid products with known geometric and radiometric characteristics. Key results include stability of dark current during cruise to within 1 data number; stability of the flat field to within the limits of inflight detectability; absolute radiometric accuracy of ∼5%, with no evident systematic change with time; validation of the focal length with an inflight measurement of 166.85 mm, compared to 167.0±0.2 mm derived onground; measurement of coalignment with the near-infrared spectrometer under flight conditions; and quantification of the intensity and distribution of scattered light.

Radiation effects on the proportional counter X-ray detectors on board the NEAR spacecraft

The X-ray proportional counters on board the Near Earth Asteroid Rendezvous (NEAR) spacecraft have exhibited a resolution degradation and recovery phenomenon several times during the long cruise phase of the mission. The resolution is checked periodically by commanding an 55Fe source into the window area. The degradation is seen as a low energy tailing of the 5.9 keV photopeak. Two events have occurred which provided good spectral data for better understanding the degradation phenomenon. In November 1997 a large solar particle event occurred that degraded the resolution and excited copper in the collimator. Eventually the detectors returned to normal. In January 1998 the spacecraft performed an Earth swingby gravity assist maneuver. The near Earth environment excited the magnesium and aluminum in the filter elements. The copper line was also produced. The NEAR spacecraft was launched in February 1996 and will rendezvous and orbit the asteroid 433 Eros in early 1999.

NEAR swings by Earth en route to Eros

The Near Earth Asteroid Rendezvous spacecraft (NEAR) conducted a swingby of Earth on January 23, 1998, en route to its final destination, the asteroid 433 Eros. The spacecraft, built and managed by the Applied Physics Laboratory of Johns Hopkins University in Laurel, Maryland, and launched February 17, 1996, aboard a Delta II‐7925‐8 rocket from Cape Canaveral, is on a mission to further our understanding of the nature of asteroids and their role in the formation of the solar system. The spacecraft is three‐axis stabilized, passively cooled, and uses four fixed solar panels to power five scientific instruments and transmit data to Earth through a 1.5 m, fixed, high‐gain antenna.As the first NASA Discovery‐class mission, NEAR was designed to return the maximum amount of information on a timely basis with minimal cost. Aside from the transponder that will be used to determine Eros' mass and gravity field, the science instruments are focused on understanding the geology, chemistry, and history of the target asteroid. The seven‐band Multi‐Spectral Imager (MSI), covering wavelengths of 0.5 to 1.1 microns, will image the entire surface of the 40 x 14 x 14 km (25 x 9 x 9 mi) asteroid, mapping its morphology and color [Hawkins et al., 1997]. The Near Infrared Spectrometer (NIS) will map out Eros' surface mineralogy using reflected sunlight in the 0.8 to 2.5 micron range [Warren et al., 1997], while the X ray/Gamma ray Spectrometers (XGRS) will determine surface elemental composition of key rock‐forming species such as Mg, Al, Si, S, Ca, Fe, Ti, and K [Goldsten et al., 1997]. The NEAR magnetometer will characterize the intensity and structure of any intrinsic magnetization of Eros [Lohr et al., 1997]. Finally, the NEAR Laser Rangefinder (NLR) altimeter will measure the asteroid's topography and shape to 1 m vertical resolution with its infrared 15 mJ pulsed beam [Cole et al., 1997].

REDUCING MISSION OPERATIONS COSTS THROUGH SPACECRAFT AUTONOMY: THE NEAR EARTH ASTEROID RENDEZVOUS (NEAR) EXPERIENCE

With a maximum time of 12 days out of ground contact and a round-trip light time as high as 56 minutes, The Near Earth Asteroid Rendezvous (NEAR) spacecraft requires a moderate degree of onboard autonomy to react to faults and safe the spacecraft. Beyond the basic safing requirements, additional functions are carried out onboard. For example, on-board calculation of the Sun, Earth, asteroid, and spacecraft positions allow the spacecraft to autonomously orient itself for science and downlink operations. On-board autonomous momentum management during cruise relieves Mission Operations from planning, scheduling, and carrying out many manual momentum dumps. During development, additional operations, such as center-of-mass management during propulsive maneuvers and optical navigation were also considered for onboard autonomy on the NEAR spacecraft, but were not selected. The allocation of functions to onboard software or to ground operations involved tradeoffs such as development time for onboard software versus ground software, resource management, life cycle costs, and spacecraft safety. After two years of cruise operations, considerable experience with the NEAR autonomy system has accrued. The utility of some autonomous capabilities is greater than expected, others less so. Software uploads increased spacecraft autonomy in some cases, and the impact on Mission Operations can be assessed. Allocation of functions between spacecraft autonomy and ground operation during development of future missions can be improved by applying the lessons learned from the NEAR experience.

Compositional mapping with the NEAR X ray/gamma ray spectrometer

The X ray/gamma ray spectrometer (XGRS) instrument on board the Near Earth Asteroid Rendezvous (NEAR) spacecraft will map asteroid 433 Eros in the 0.7 keV to 10 MeV energy region. Measurements of the discrete line X ray and gamma ray emissions in this energy domain can be used to obtain both qualitative and quantitative elemental compositions with sufficient accuracy to enable comparison to the major meteorite typies. It is believed that Eros is an S‐type asteroid, the most common of the near‐Earth asteroids. The determination of whether Eros consists of either differentiated or undifferentiated materials is an important objective of this mission. Observations of Eros during the NEAR mission will contribute significantly to our understanding of the structure and composition of this asteroid. The NEAR spacecraft was successfully launched on February 17, 1996. The NEAR XGRS was turned on during the week of April 7, 1996, and all detector systems operated nominally. Background spectra have been obtained.

The NEAR laser ranging investigation

The objective of the Near‐Earth Asteroid Rendezvous (NEAR) laser ranging investigation is to obtain high integrity profiles and grids of topography for use in geophysical, geodetic and geological studies of asteroid 433 Eros. The NEAR laser rangefinder (NLR) will determine the slant range of the NEAR spacecraft to the asteroid surface by measuring precisely the round trip time of flight of individual laser pulses. Ranges will be converted to planetary radii measured with respect to the asteroid center of mass by subtracting the spacecraft orbit determined from X band Doppler tracking. The principal components of the NLR include a 1064 nm Cr:Nd:YAG laser, a gold‐coated aluminum Dall‐Kirkham Cassegrain telescope, an enhanced silicon avalanche photodiode hybrid detector, a 480‐MHz crystal oscillator, and a digital processing unit. The instrument has a continuous in‐flight calibration capability using a fiber‐optic delay assembly. The single shot vertical resolution of the NLR is <6 m, and the absolute accuracy of the global grid will be ∼ 10 m with respect to the asteroid center of mass. For the current mission orbital scenario, the laser spot size on the surface of Eros will vary from ∼4–11 m, and the along‐track resolution for the nominal pulse repetition rate of 1 Hz will be approximately comparable to the spot size, resulting in contiguous along‐track profiles. The across‐track resolution will depend on the orbital mapping scenario, but will likely be <500 m, which will define the spatial resolution of the global topographic model. Planned science investigations include global‐scale analyses related to collisional and impact history and internal density distribution that utilize topographic grids as well as spherical harmonic topographic models that will be analyzed jointly with gravity at commensurate resolution. Attempts will be made to detect possible subtle time variations in internal structure that may be present if Eros is not a single coherent body, by analysis of low degree and order spherical harmonic coefficients. Local‐ to regional‐scale analyses will utilize high‐resolution three‐dimensional topographic maps of specific surface structures to address surface geologic processses. Results from the NLR investigation will contribute significantly to understanding the origin, structure, and evolution of Eros and other asteroidal bodies.

The NEAR Radio Science investigations

The science objectives for the Near‐Earth Asteroid Rendezvous (NEAR) Radio Science team include determining the masses of asteroids 253 Mathilde (to within 10%) and 433 Eros (<0.1%). While the NEAR spacecraft is in orbit about Eros, the radiometric spacecraft tracking data, the optical landmark tracking data, and the lidar altimetry measurements will be used to determine the gravity field of Eros. Comparisons of this gravity field with one determined from Eros shape models (assuming constant density) will provide constraints upon the internal structure of this asteroid. In addition, the spin state, principal axes, and moments of inertia will be determined as part of the Radio Science activities. A campaign to meet the radio science objectives will require the close cooperation of the NEAR Navigation, Imaging, and Lidar teams.

Postlaunch Contingency Trajectories for the Near-Earth Asteroid Rendezvous Mission

The August 1995 Koreasat 1 Delta II launch vehicle failure pointed to the prudence of developing a postlaunch contingency strategy for varying levels of Delta II launch vehicle failure. The objective of this investigation is to deŽ ne contingency strategies that maximize accomplishment of the Near-Earth Asteroid Rendezvous mission objectives. The baseline mission incorporates a trajectory correction maneuver at one week after launch,  yby of main belt asteroid (253) Mathilde in June 1997, and rendezvous with near-Earth asteroid (433) Eros in February 1999.After a partial launch vehicle failure for the Near-Earth Asteroid Rendezvous spacecraft, the need to reduce D V penalties associated with a delayed initial trajectory correction maneuver would require mission planners to quickly formulate a contingency trajectory design. Therefore, postlaunch contingency trajectories were designed prior to launch to avoid selection of a less-than-optimal alternative mission option resulting from emergency contingency planning after launch. Strategies were deŽ ned for how to perform the initial trajectory correction for launch vehicle failure approaching twice the velocity shortfall experienced by Koreasat 1. These strategies enable completionofmostmissionobjectives with 1) rendezvouswith Eros after an injection velocity shortfall up to 69m/s and 2) rendezvouswith near-Earth asteroid (4660)Nereus in 2003 after an injection velocity shortfall up to 300m/s.

Multi-Spectral Imager On the Near Earth Asteroid Rendezvous Mission

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.

Overview of the Multi-Spectral Imager on the NEAR spacecraft

The Multi-Spectral Imager on the Near Earth Asteroid Rendezvous (NEAR) spacecraft is a 1 Hz frame rate CCD camera sensitive in the visible and near infrared bands (~400−1100 nm). MSI is the primary instrument on the spacecraft to determine morphology and composition of the surface of asteroid 433 Eros. In addition, the camera will be used to assist in navigation to the asteroid. The instrument uses refractive optics and has an eight position spectral filter wheel to select different wavelength bands. The MSI optical focal length of 168 mm gives a 2.9 ° × 2.25 ° field of view. The CCD is passively cooled and the 537×244 pixel array output is digitized to 12 bits. Electronic shuttering increases the effective dynamic range of the instrument by more than a factor of 100. A one-time deployable cover protects the instrument during ground testing operations and launch. A reduced aperture viewport permits full field of view imaging while the cover is in place. A Data Processing Unit (DPU) provides the digital interface between the spacecraft and the Camera Head and uses an RTX2010 processor. The DPU provides an eight frame image buffer, lossy and lossless data compression routines, and automatic exposure control. An overview of the instrument is presented and design parameters and trade-offs are discussed.

Groundbased Reconnaissance of Asteroid 253 Mathilde: Visible Wavelength Spectrum and Meteorite Comparison

Asteroid 253 Mathilde has been identified as a flyby target for the near-Earth asteroid rendezvous spacecraft enroute to 433 Eros. We performed 4300- to 9200-Å spectroscopy of Mathilde and found it to be a C-class asteroid, an asteroid type not yet visited by a spacecraft. We also compare Mathilde's spectrum to similar meteorite analogs such as carbonaceous chondrites and black ordinary chondrites.

Mission to the sun: The Solar Pioneer

The Solar Pioneer is a mission concept developed by the Johns Hopkins University Applied Physics Laboratory (JHU/APL) to do exploratory science in the inner heliosphere and outer solar corona. The concept is derived from the Near Earth Asteroid Rendezvous (NEAR) spacecraft now being built by JHU/APL for NASA and draws upon that design to the maximum extent possible. The primary purpose, to conduct an exploratory in situ basic science investigation, has been focused to emphasize in situ particles and fields measurements of the outer solar corona and inner solar wind region. The purpose of the Solar Pioneer is to deliver a payload of scientific instruments to approximately 4 solar radii. The basic characteristics of the JHU/APL baseline concept provide for delivery of 30 to 50 kg of scientific payload to 4 R s while maintaining a high data rate. Life-cycle cost control is obtained by: (1) focusing on prime science objectives, (2) applying advanced technology where it makes sense, and (3) capitalizing on developed subsystems derived from the NEAR spacecraft. By implementing a focused strategy from science goals through all stages of program management, such a mission can be carried out for less than one quarter of previous Solar Probe mission cost estimates.

Mission to the sun: The solar pioneer

The Solar Pioneer is a mission concept developed by the Johns Hopkins University Applied Physics Laboratory (JHU/APL) to do exploratory science in the inner heliosphere and outer solar corona. The concept is derived from the Near Earth Asteroid Rendezvous (NEAR) spacecraft now being built by JHU/APL for NASA. The purpose of the Solar Pioneer is to deliver a payload of scientific instruments to approximately 4 solar radii (Rs - 3 radii above the visible solar surface or photosphere).The Solar Probe concept has evolved since its original introduction to the scientific community in 19781 while the key science questions to be answered have changed little. The primary purpose, to conduct an exploratory in situ basic science investigation, has been focused to emphasize in situ particles and fields measurements of the outer solar corona and inner solar wind region. Key science goals of the probe mission include the determination of:(1)how the solar wind is heated and accelerated,(2)where different types of solar wind come from,(3)how solar energetic particles (SEP) are accelerated, and(4)the nature of the unique plasma turbulence near the sun.The basic characteristics of the JHU/APL baseline concept provide for delivery of 42 to 60 kg of scientific payload to 4 Rs while maintaining a high data rate of 30 kilobits per second (kbps) at 1 astronomical unit (AU) (X-band downlink to 70 meter antenna of the Deep Space Network). The baseline design draws upon the NEAR spacecraft and subsystem design to the maximum extent possible. The baselined launch vehicle is an Atlas IIA with a Star48 insertion stage system. Life-cycle cost control is obtained by:(1)focusing on prime science objectives,(2)applying advanced technology where it makes sense, and(3)capitalizing on developed subsystems derived from the NEAR spacecraftThe Solar Pioneer is designed to solve questions of basic physics about the solar environment, enabling the solution to applied questions of the effects of the sun and solar cycle on the Earth and human society. By implementing a focused strategy from science goals through all stages of program management, such a mission can be carried out for less than one quarter of previous Solar Probe mission cost estimates2,3