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NASA NTRS2006

The Preliminary Examination of Organics in the Returned Stardust Samples from Comet Wild 2

The primary objective of STARDUST is to collect coma samples from comet 8lP/Wild 2. These samples were collected by impact onto aerogel tiles on Jan 2, 2004 when the spacecraft flew through the comet's coma at a relative velocity of about 6.1 km/sec. Measurements of dust impacts on the front of the spacecraft suggest that the aerogel particle collector was impacted by 2800 +/- 500 particles larger than 15 micron in diameter. Following recovery of the Sample Return Capsule (SRC) on Jan 15, 2006, the aerogel collector trays will be removed in a clean room at JSC. After documentation of the collection, selected aerogel tiles will be removed and aerogel and cometary samples will be extracted for study. A number of different extraction techniques will be used, each optimized for the analytical technique that is to be used. The STARDUST Mission will carry out a 6 month preliminary examination (PE) of a small portion of the returned samples. The examination of the samples will be made by a number of subteams that will concentrate on specific aspects of the samples. One of these is the Organics PE Team (see the author list above for team members). These team members will use a number of analytical techniques to produce a preliminary characterization of the abundance and nature of the organics (if any) in the returned samples.

Sandford, S. A.↗
NASA NTRS2004

NASA STARDUST Sample Return Mission

This viewgraph presentation reviews the Stardust mission. The objectives of the mission is to rendezvous with the Wild 2 comet, and using a specially designed aerogel capture some of the cometary material, and then return a capsule with the material to Earth. Other objectives are to provide images of the comet, and capture interstellar dust. There is a description of the aerogel, the trajectory, and views of the Stardust Sample Return Capsule (SRC), Cometary and Interstellar Dust Analyzer (CIDA) instrument, and the JPL designed camera. Also included is a timeline of the projected release of data to the Planetary Data System.

Wild 2↗
NASA NTRSDate not supplied

Sample Return and Preliminary Examination Timeline for the OSIRIS-REx Mission

NASA’s OSIRIS-REx spacecraft collected a sample of asteroid (101955) Bennu on October 20, 2020, using the Touch-and-Go Sample Acquisition Mechanism (TAGSAM) [1,2,3]. After sample acquisition, the TAGSAM collection head was stowed in the Sample Return Capsule (SRC; Fig. 1) for transport back to Earth. On September 24, 2023, the OSIRIS-Rex spacecraft will fly by Earth and release the SRC, which will land at the Utah Test and Training Range (UTTR). The sample will be transported to the OSIRIS-REx curation facility, located within NASA’s Johnson Space Center (JSC), where it will be examined, cataloged, and allocated for scientific analyses. Here we describe the timeline of operations for the return, recovery, and initial characterization of the Bennu sample.

Asteroid↗
NASA NTRS1990

The Genesis Solar Wind Sample Return Mission

The Genesis spacecraft was launched on August 8 from Cape Canaveral on a journey to become the first spacecraft to return from interplanetary space. The fifth in NASA's line of low-cost Discovery-class missions, its goal is to collect samples of solar wind and return them to Earth for detailed isotopic and elemental analysis. The spacecraft is to collect solar wind for over two years, while circling the L1 point 1.5 million km sunward of the earth, before heading back for a capsule-style re-entry in September, 2004. After parachute deployment, a mid-air helicopter recovery will be used to avoid a hard landing. The mission has been in the planning stages for over ten years. Its cost, including development, mission operations, and sample analysis, is approximately $209M. The Genesis science team, headed by principal investigator Donald Burnett of Caltech, consists of approximately 20 co-investigators from universities and science centers around the country and internationally. The spacecraft consists of a relatively flat spacecraft bus containing most of the subsystem components, situated below a sample return capsule (SRC) which holds the solar-wind collection substrates and an electrostatic solar wind concentrator. Some of the collectors are exposed throughout the collection period, for a sample of bulk solar wind, while others are exposed only to certain solar wind regimes, or types of flow. Ion and electron spectrometers feed raw data to the spacecraft control and data-handling (C&DH) unit, which determines ion moments and electron flux geometries in real time. An algorithm is used to robotically decide between interstream (IS), coronal hole (CH), and coronal mass ejection (CME) regimes, and to control deployment of the proper arrays to sample these wind regimes independently. This is the first time such a solar-wind decision algorithm has been used on board a spacecraft.

Wiens, Roger C.↗
NASA NTRS2007

Overview of the Results of the Organics PET Study of the Cometary Samples from Comet Wild 2 by the Stardust Mission

STARDUST is the first mission designed to bring samples back to Earth from a known comet. The captured samples were successfully returned to Earth on 15 Jan 2006, after which they were subjected to a preliminary examination by a number of teams of scientists from around the world. This abstract describes the efforts of the Organics Preliminary Examination Team (PET). More detailed discussions of specific analyses of the samples can be found in other papers presented at this meeting by individual members of the Organics PET (see the author list above for team members). The studied Wild 2 gas and dust samples were collected by impact onto aerogel tiles and Al foils when the spacecraft flew through the coma of 81P/Wild 2 on 2 Jan 2004 at a relative velocity of approx.6.1 kilometers per second. After recovery of the Sample Return Capsule (SRC) on 15 Jan 2006, the aerogel collector trays were removed in a clean room at JSC. After documentation of the collection, selected aerogel tiles and aluminum foils were removed and aerogel and cometary samples extracted for study.

Sandford, S. A.↗
NASA NTRS2005

Genesis Recovery Processing

The Genesis spacecraft, launched in August 2001 to collect samples of the solar wind, returned to Earth on 8 September 2004. The Sample Return Capsule (SRC) failed to deploy its drogue parachute and parafoil and subsequently impacted the Utah Test and Training Range (UTTR) at an estimated 310 kph (193 mph). The goal of the Genesis mission to collect and return samples of the solar wind for precise elemental and isotopic analysis provides the scientific community with a unique set of materials to aid in understanding the origin of our solar system. The spacecraft orbited the Earth-Sun L1 point for 29 months exposing a suite of fifteen types of ultrapure, ultraclean materials in several different locations. Most of the materials were mounted on fixed or deployable wafer panels called collector arrays . A few materials were mounted as targets in the focal spot of an electrostatic mirror (the concentrator ). Other materials were strategically placed to maximize the area for solar-wind collection.

Stansbery, E. K.↗
NASA NTRS2014

OSIRIS-REx Touch-and-Go (TAG) Mission Design for Asteroid Sample Collection

The Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) mission is a NASA New Frontiers mission launching in September 2016 to rendezvous with the near-Earth asteroid Bennu in October 2018. After several months of proximity operations to characterize the asteroid, OSIRIS-REx flies a Touch-And-Go (TAG) trajectory to the asteroid's surface to collect at least 60 g of pristine regolith sample for Earth return. This paper provides mission and flight system overviews, with more details on the TAG mission design and key events that occur to safely and successfully collect the sample. An overview of the navigation performed relative to a chosen sample site, along with the maneuvers to reach the desired site is described. Safety monitoring during descent is performed with onboard sensors providing an option to abort, troubleshoot, and try again if necessary. Sample collection occurs using a collection device at the end of an articulating robotic arm during a brief five second contact period, while a constant force spring mechanism in the arm assists to rebound the spacecraft away from the surface. Finally, the sample is measured quantitatively utilizing the law of conservation of angular momentum, along with qualitative data from imagery of the sampling device. Upon sample mass verification, the arm places the sample into the Stardust-heritage Sample Return Capsule (SRC) for return to Earth in September 2023.

OSIRIS-REX TOUCH-AND-GO (TAG) MISSION DESIGN FOR A↗
NASA NTRSDate not supplied

OSIRIS-REx Screening Experience & Lessons Learned

On September 24, 2023, the NASA OSIRIS-REx spacecraft returned a sample of asteroid Bennu, approaching on a hyperbolic impact trajectory relative to Earth. At approximately 108,000 km altitude and four hours prior to hitting the top of the atmosphere, the Sample Return Capsule (SRC) separated from the spacecraft bus, targeting the Utah Test and Training Range. Twenty minutes later, the bus performed a large divert maneuver to fly by at a perigee altitude of ~780 km. Given the immense scientific value of the sample, substantial efforts were undertaken by NASA CARA and the OSIRIS-REx mission to ensure safe passage of the objects from GEO through LEO. This presentation provides an overview of collision avoidance maneuver (CAM) options, results of screenings, coordination with DoD for contingency observations, and lessons learned for screening future Earth flyby and entry trajectories. Two particular challenges included screening two objects using a much larger than normal 250 km spherical monitor volume and decision planning for a single CAM while the SRC was still attached that would alter both trajectories. The larger, non-standard screening volume resulted in custom procedures that CARA personnel had to run manually for each screening, and the initial long propagation times while the objects were more than a week out required significant computing resources. With a single CAM opportunity at 13 hours out, the decision to execute a maneuver had to consider the risk to both objects, where one could imagine a situation where the maneuver would clear a high-risk conjunction for one object and introduce one for the other – begging the question of relative risk posture between the SRC and bus. These among other unique aspects of Earth flyby and entry missions led to novel planning and implementation procedures to support future missions of this type.

Dolan E. Highsmith↗
NASA NTRS2019

Outgassing From the OSIRIS-REx Sample Return Capsule: Characterization and Mitigation

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft launched on September 8, 2016, beginning a seven-year journey to return at least 60 g of asteroid material from (101955) Bennu to Earth. During the outbound cruise, Doppler tracking of the spacecraft observed a small but measurable acceleration when the sample return capsule (SRC) was first placed in sunlight. Subsequent analysis determined that outgassing from the SRC is the most likely cause for the acceleration. This outgassing received combined engineering and scientific attention because it has potential implications both for spacecraft navigation performance and for contamination of the collected samples. Thermal modeling, laboratory studies of SRC materials, and monitoring of the acceleration are all consistent with H2O as the main component of the outgassing. Dedicated, in-flight campaigns continued to expose the SRC to sunlight until the acceleration dropped to the acceleration noise floor. Any residual amounts of H2O outgassing are not considered to be a hazard with regards to mission operations or pristine sample acquisition. The sample stow procedure has been updated to ensure that no direct line of site exists between any residual outgassing and the samples during future operations. Similar outgassing of the Stardust SRC probably also occurred. No adverse contamination of Stardust samples was observed that could be associated with this process. Future missions that use similar reentry vehicles should consider procedures to test for and, if necessary, mediate such outgassing after launch.

Origins, Spectral Interpretation, Resource Identif↗
NASA NTRS2019

Outgassing From the OSIRIS-REx Sample Return Capsule: Characterization and Mitigation

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft launched on September 8, 2016, beginning a seven-year journey to return at least 60 g of asteroid material from (101955) Bennu to Earth. During the outboundcruise, Doppler tracking of the spacecraft observed a small but measurable acceleration when the sample return capsule (SRC) was first placed in sunlight. Subsequent analysis determined that outgassing from the SRC is the most likely cause for the acceleration. This outgassing received combined engineering and scientific attention because it has potential implications both for spacecraft navigation performance and for contamination of the collected samples. Thermal modeling, laboratory studies of SRC materials, and monitoring of the acceleration are all consistent with H2O as the main component of the outgassing. Dedicated, in-flight campaigns continued to expose the SRC to sunlight until the acceleration dropped to the acceleration noise floor. Any residual amounts of H2O outgassing are not considered to be a hazard with regards to mission operations or pristine sample acquisition. The sample stow procedure has been updated to ensure that no direct line of site exists between any residual outgassing and the samples during future operations. Similar outgassing of the Stardust SRC probably also occurred. No adverse contamination of Stardust samples was observed that could be associated with this process. Future missions that use similar reentry vehicles should consider procedures to test for and, if necessary, mediate such outgassing after launch.

Scott A Sandford↗
NASA NTRS2024

2023 Cleanroom Monitoring for OSIRIS-REx

OSIRIS-REx is an asteroid sample return mission that delivered asteroid regolith from Bennu to Earth on 9/24/2023 [1]. Cleanroom monitoring of OSIRIS-REx Curation facilities has been ongoing since 2021 when construction of the OSIRIS-REx lab at Johnson Space Center (JSC) was completed [2]. The monitoring continues inside of the OSIRIS-REx lab in Houston. Monitoring was also conducted on a temporary cleanroom constructed inside a hangar at the Utah Test and Training Range (UTTR) to initially receive the Sample Return Capsule (SRC) upon its landing there. The following reports on cleanroom monitoring that has taken place in the months leading up to as well as after OSIRIS-REx return. Monitoring techniques used include particle counts, deployment of Si wafer witness plates (Balazs, Inc.) and Al foil witness plates, gas sampling (Balazs, Inc.) and microbiological monitoring. We collected particle counts at both the lab at JSC as well as the temporary cleanroom at UTTR. Particle counts were taken monthly from six locations in the lab at JSC. Particle counts were taken from seven locations at UTTR in July, August, and September. The UTTR cleanroom particle counts were taken daily in the five days leading to OSIRIS-REx return as well as consistently the day of return (every 2 minutes and 15 seconds 7:21 am- 6:27 pm) from one location inside the cleanroom. The particle counts at UTTR consistently stayed well within the ranges of its required ISO 7 equivalent classification (352,000 maximum particles/ m3 ≥ 0.5 μm). Most analysis showed that the particle counts were far below ISO 7 requirements (highest measured count was 61,484 particles/ m3 ≥ 0.5 um). but the elevated instances correlated to exterior hangar doors being open. Particle counts were reduced when keeping exterior hangar doors closed. The particle counts at JSC have stayed consistently within their ISO 5 equivalent classification (3,520 maximum particles/ m3 ≥ 0.5 um). In most instances, the counts are much better except in one instance where the count measured 13,381 particles/ m3 ≥ 0.5 um. The high spike in particle counts in the JSC lab correlated with the air handlers being shut down temporarily the previous day. The particle counts taken in the same location quickly reduced and measured 0 when taken a month later with the air handlers on. We deployed 8-inch semiconductor polished Si wafer witness plates for 24-hour periods inside of the OSIRIS-REx Curation lab at JSC (in July, August, September, and November 2023) and the cleanroom at UTTR (July and September 2023) to test for possible organic and inorganic contaminants. We also deployed these wafers inside of the OSIRIS-REx Touch-and-Go sample Acquisition Mechanism (TAGSAM) glovebox (where Bennu sample processing occurs) and desiccator (Bennu sample storage) at JSC in August 2023. These samples were all sent to Balazs for analysis via Thermal Desorption Gas Chromatography Mass Spectroscopy (TD-GC-MS) to quantify organic compounds and vapor phase decomposition inductively coupled plasma mass spectrometry (VPD-ICP-MS) to quantify inorganic contaminants. We collected air samples using an adsorbent tube connected to a pump for six hours (100 mL/minute) inside of both the JSC lab and the UTTR cleanroom. These samples were taken at JSC in July, August, September, November, and December and at UTTR in July and September. Additionally, a sample was taken just outside of the TAGSAM glovebox airlock door in July. These samples were sent to Balazs for analysis of volatile organics in air. Overall, the OSIRIS-REx lab at JSC and cleanroom at UTTR yielded very low organic and inorganic contaminants (similar results to Genesis lab at JSC which is ISO 4 equivalent) except for boron, which is attributed to the borosilicate glass in the fan filter units. We collected monthly surface and air samples inside the JSC lab to monitor potential microbial contamination. We report the recovery rate for each sampling event, which is defined as the number of samples exhibiting bacterial or fungal growth divided by the total number of samples collected. Since the lab was commissioned in 2021 the median recovery rate is 29%. This recovery rate is consistent with other ISO 5 equivalent labs used to curate astromaterials collections. Increases in recovery rate correspond to construction and/or extra activity in the lab. However, increases in recovery rate do not reliably correlate to increases in particle counts, which highlights the need for a dedicated microbial monitoring program for biologically sensitive collections. We sampled the temporary clean room at UTTR in July, August, and September of 2023 to monitor potential microbial contamination. The recovery rate decreased from 80% in August to 29% in September. However, in all instances, the diversity of bacteria and fungi was higher in the UTTR cleanroom than in the JSC lab. We routinely collected more than twenty different organisms from the UTTR cleanroom. In the JSC lab the median diversity is 2 organisms. Based on these results we hypothesize that microbes from UTTR could be transported back to JSC with the Bennu samples. To mitigate this risk, in September of 2023, we implemented additional cleaning procedures in the JSC lab to reduce the bioburden on surfaces that could come into direct contact with hardware used to process Bennu samples. Since adopting these additional cleaning measures, the median recovery rate has decreased to 14%. We did not observe an increase in fungal or bacterial diversity in the lab in the October sampling. We will continue to monitor this trend closely for the next several months. Supported by NASA under Award NNH09ZDA007O and Contract NNM10AA11C.

Rachel Comstock Funk↗
NASA NTRSDate not supplied

OSIRIS-REx Off-Nominal Re-entry Breakup Analysis

The Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) is a NASA asteroid sampling mission that launched on September 8, 2016. Its objectives are to study the asteroid Bennu for up to 505 days and obtain at least 60 grams of pristine regolith. The sample return to Earth is planned for September 2023. For contingency planning and risk assessment of a potential off-nominal Earth-return trajectory, a re-entry breakup analysis was performed to determine the response of the spacecraft to the environment and predict the breakup sequence and timeline, debris survival, and debris impact conditions. The failure scenario assumed a failure to separate between the bus and the sample return capsule (SRC), resulting in the combined bus+SRC configuration for the re-entry vehicle. Furthermore, consistent overburns or underburns were considered to produce three sets of initial conditions for the analysis consisting of nominal, steep, and shallow entry flight path angles. The results were compared to the breakup analysis performed for a similar vehicle, the Stardust spacecraft, which returned samples from the comet Wild 2 in 2006. This paper describes the OSIRIS-REx spacecraft and presents the results of the re-entry breakup analysis.

reentry breakup analysis↗
NASA NTRSDate not supplied

Extensibility of PICA TPS for Future Sample Return Missions

Stardust was the first successful robotic sample return mission delivering samples of the Comet Wild 2 to Earth in 2006. Genesis followed Stardust, in the era of “faster, better, cheaper,” collecting samples of solar wind. The Genesis sample return capsule (SRC) was larger and the program did not have the time nor funding to scale up the Stardust PICA heatshield and so, utilized an alternate heatshield. The successful Stardust mission led to future mission concepts baselining Stardust EDL, especially the entry heatshield. OSIRIS REx, was one such concept and the mission was designed to include build-to-print elements of the Stardust design. The primary scale-up limitation beyond Stardust and OSIRIS REx is the single-piece net cast PICA heatshield. In the past three years, FMI working with NASA Ames, expanded the manufacturing capability of PICA and demonstrated a 1.3 m PICA single piece TPS. This was done in anticipation of the Mars Sample Return mission as well as future Sample Return missions requiring larger-scale SRCs. This effort also identified a sustainable domestic replacement precursor for the PICA preform as the heritage precursor was discontinued in 2016 and FMI has gone through multiple rayon replacements since Stardust. As part of the effort, PICA was also tested at conditions higher than the Stardust or OSIRIS REx entry envelope to establish an expanded performance envelope and enable future sample return missions at higher entry speeds. The poster will highlight PICA sustainability and extensibility as part of the Sample Return to Earth session.

PICA thermal protection↗
NASA NTRSDate not supplied

OSIRIS-REx Earth Return & Entry: Navigation Operations & Lessons Learned

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft successfully returned to Earth on September24, 2024, safely delivering its Sample Return Capsule (SRC) to the Utah Test and Training Range (UTTR). This paper describes the navigation operations that occurred between the departure from Bennu and the return of the SRC. An overview is given of the Flight Dynamics System (FDS) that includes tracking, orbit determination (OD), maneuver planning, and interfaces with entry, descent, and landing. Operational details on the SRC release criteria and conjunction assessment considerations are also provided. Lessons learned are presented that may help future sample return or interplanetary entry missions.

Kenneth M. Getzandanner↗
NASA NTRS2007

Genesis Concentrator Target Particle Contamination Mapping and Material Identification

The majority of surface particles were found to be < 5 microns in diameter with increasing numbers close to the optical resolution limit of 0.3 microns. Acceleration grid EDS results show that the majority of materials appear to be from the SRC shell and SLA materials which include carbon-carbon fibers and Si-rich microspheres in a possible silicone binder. Other major debris material from the SRC included white paint, kapton, collector array fragments, and Al. Image analysis also revealed that SRC materials were also found mixed with the Utah mud and salt deposits. The EDS analysis of the acceleration grid showed that particles < 1 m where generally carbon based particles. Chemical cleaning techniques with Xylene and HF in an ultrasonic bath are currently being investigated for removal of small particles by the Genesis science team as well as ultra-pure water megasonic cleaning by the JSC team [4]. Removal of organic contamination from target materials is also being investigated by the science team with the use of UV-ozone cleaning devices at JSC and Open University [5]. In preparation for solar wind oxygen analyses at UCLA and Open University [1, 2], surface particle contamination on three Genesis concentrator targets was closely examined to evaluate cleaning strategies. Two silicon carbide (Genesis sample # 60001 and 60003) and one chemical vapor deposited (CVD) 13C concentrator target (60002) were imaged and mosaic mapped with optical microscopes. The resulting full target mosaic images and particle feature maps were subsequently compared with non-flight, but flight-like, concentrator targets and sample return capsule (SRC) materials. Contamination found on the flown concentrator acceleration grid was further examined using a scanning electron microscope (SEM). Energy dispersive X-ray spectroscopy (EDS) for particle identification was subsequently compared with the optical images from the flown targets. Figure 1 show that all three targets imaged in this report are fully intact and do not show any signs of material fractures. However, previous ellipsometry results and overview imaging of both flown SiC targets show a solar wind irradiation gradient from the center focal point to the outer edge [3]. In addition, due to the hard landing, each target has experienced varying degrees of impacts, scratches, and particle debris from the spacecraft and Utah impact site.

Calaway, Michael J.↗
NASA NTRS2014

Stardust Interstellar Preliminary Examination V: XRF Analyses of Interstellar Dust Candidates at ESRF ID13

Here, we report analyses by synchrotron X-ray fluorescence microscopy of the elemental composition of eight candidate impact features extracted from the Stardust Interstellar Dust Collector (SIDC). Six of the features were unambiguous tracks, and two were crater-like features. Five of the tracks are so-called midnight tracks that is, they had trajectories consistent with an origin either in the interstellar dust stream or as secondaries from impacts on the Sample Return Capsule (SRC). In a companion paper reporting synchrotron X-ray diffraction analyses of ISPE candidates, we show that two of these particles contain natural crystalline materials: the terminal particle of track 30contains olivine and spinel, and the terminal particle of track 34 contains olivine. Here, we show that the terminal particle of track 30, Orion, shows elemental abundances, normalized to Fe, that are close to CI values, and a complex, fine-grained structure. The terminal particle of track 34, Hylabrook, shows abundances that deviate strongly from CI, but shows little fine structure and is nearly homogenous. The terminal particles of other midnight tracks, 29 and 37, had heavy element abundances below detection threshold. A third, track28, showed a composition inconsistent with an extraterrestrial origin, but also inconsistent with known spacecraft materials. A sixth track, with a trajectory consistent with secondary ejecta from an impact on one of the spacecraft solar panels, contains abundant Ce and Zn. This is consistent with the known composition of the glass covering the solar panel. Neither crater-like feature is likely to be associated with extraterrestrial materials. We also analyzed blank aerogel samples to characterize background and variability between aerogel tiles. We found significant differences in contamination levels and compositions, emphasizing the need for local background subtraction for accurate quantification.

Stardust↗
NASA NTRS2000

Stardust Navigation Covariance Analysis

The Stardust spacecraft was launched on February 7, 1999 aboard a Boeing Delta-II rocket. Mission participants include the National Aeronautics and Space Administration (NASA), the Jet Propulsion Laboratory (JPL), Lockheed Martin Astronautics (LMA) and the University of Washington. The primary objective of the mission is to collect in-situ samples of the coma of comet Wild-2 and return those samples to the Earth for analysis. Mission design and operational navigation for Stardust is performed by the Jet Propulsion Laboratory (JPL). This paper will describe the extensive JPL effort in support of the Stardust pre-launch analysis of the orbit determination component of the mission covariance study. A description of the mission and it's trajectory will be provided first, followed by a discussion of the covariance procedure and models. Predicted accuracy's will be examined as they relate to navigation delivery requirements for specific critical events during the mission. Stardust was launched into a heliocentric trajectory in early 1999. It will perform an Earth Gravity Assist (EGA) on January 15, 2001 to acquire an orbit for the eventual rendezvous with comet Wild-2. The spacecraft will fly through the coma (atmosphere) on the dayside of Wild-2 on January 2, 2004. At that time samples will be obtained using an aerogel collector. After the comet encounter Stardust will return to Earth when the Sample Return Capsule (SRC) will separate and land at the Utah Test Site (UTTR) on January 15, 2006. The spacecraft will however be deflected off into a heliocentric orbit. The mission is divided into three phases for the covariance analysis. They are 1) Launch to EGA, 2) EGA to Wild-2 encounter and 3) Wild-2 encounter to Earth reentry. Orbit determination assumptions for each phase are provided. These include estimated and consider parameters and their associated a-priori uncertainties. Major perturbations to the trajectory include 19 deterministic and statistical maneuvers planned for the mission. The spacecraft is three axis stabilized and has unbalanced thrusters for attitude control. Accelerations due to the attitude control system are treated stochastically. The tracking scenario for the study is patterned after the actual schedule employed during the different phases of the mission. Conventional X-band two-way Doppler and SRA range data was simulated and the standard accuracy for these data types was assumed throughout most of the mission. However, a deweighting scheme was used for the Doppler data during times of low Sun-Earth-Probe angles, especially in the case of the DSM. Optical data is assumed to be available starting at 50 days prior to the comet encounter. The optical data will be used to improve the ephemeris of Wild-2, which is considered crucial to properly target the comet flyby. Results of the covariance analysis are presented for all mission phases. Navigation capability will be discussed in terms of the uncertainty in the encounter B-Plane (B.R and B.T) and linearized time of flight. Delivery errors based on the final maneuver prior to the comet encounter will be presented. The most stringent navigation requirement is for the Earth reentry. The uncertainty in the flight path angle must be less than 0.02 degree (orbit determination and maneuver performance) to assure successful recovery of the SRC. Results presented show that this requirement can be met.

Menon, Premkumar R.↗
NASA NTRS1996

PICA Forebody Heatshield Qualification for the Stardust Discovery Class Mission

This paper presents the qualification of the light weight Phenolic Impregnated Carbon Ablators (PICA) as the forebody heatshield for the Stardust Discovery Class Mission. The Stardust spacecraft will be launched in early 1999 and fly by Comet Wild-2 to collect cometary and interstellar dust and return them back to earth in the Sample Return Capsule (SRC). This earth re-entry will be the fastest to date, at 12.6 km/s, and therefore requires a heatshield that can withstand very high heating rates and stagnation pressures, as well as provide the necessary insulation to the vehicle structure. The PICA material was developed as part of the Lightweight Ceramic Ablators program at NASA Ames Research Center, and was baselined as the forebody heatshield because of its low density and superior ablation and thermal performance at severe aerothermodynamic conditions. Under a Small Business Innovative Research (SBIR) program with NASA Ames, Fiber Materials, Inc. developed a process to manufacture a single-piece PICA heatshield for the forebody of the SRC, along with witness material for the fabrication of the test models. The test models were fabricated and instrumented by the staff of Lockheed Martin Astronautics in Denver, Colorado. Full body preliminary aerothermal CFD calculations were performed at NASA Ames to determine the heating and stagnation pressure conditions. The Heat shield sizing was also performed at NASA Ames by using a new material response code that accounts for the highly porous characteristics of the PICA material. The ablation and thermal performance of PICA was qualified in the NASA Ames Interaction Heating Arc Jet Facility. A total of 24 models and four test conditions were used to qualify PICA at the predicted peak heat flux, heat load, shear, and stagnation pressure conditions. Surface and in-depth temperatures were measured using optical pyrometers and thermocouples. Surface recession was measured by using a template and a height gage. Several models were tested to evaluate repair procedures, and two models were cold soaked in liquid nitrogen, prior th testing, to investigate the effect of the cold space environment on the performance of the material. In addition, material cored from a demonstration single-piece heatshield was tested to verify that the PICA process can be successfully completed on a large, complex heatshield shape.

Tran, Huy K.↗