Robert E. Lombardi

On-Orbit Error Rates of RHBD SRAMs: Comparison of Calculation Techniques and Space Environmental Models With Observed Performance

SEU data for more than 250 equivalent on-orbit SRAM device years is compared with upset rate calculations using various environmental models and contributions of both direct ionization and nuclear interactions.

Spacecraft Charging Monitoring at GEO: Natural and Electric Propulsion Environment Measurements

Surface charging sensors are used on spacecraft to characterize the potential difference between a sample material surface relative to spacecraft common ground. A review has been performed of data collected over a period representative of a typical spacecraft lifetime from more than 10 such sensors aboard 6 Lockheed Martin built satellites operated by SES and INTELSAT which employ the use of electric propulsion systems at geosynchronous altitudes. Data are used to study the effects on surface charging caused by the electric propulsion plasma / GEO plasma correlative environment. Data are also used to review the performance of the sensors, characterize worst-case charging conditions experienced by the vehicles, and evaluate the frequency of severe charging events over the mission lifetimes.

On-Orbit SEU Rates of UC1864 PWM: Comparison of Ground Based Rate Calculations and Observed Performance

More than 10 years of on-orbit UC1864 SEU data are compared with typical upset rate calculation methodologies and GCR environments. Results suggest that the most common calculation methods overestimate upset rates by at least 2×. Mitigation techniques are also verified via direct in orbit observations.

Spacecraft Charging, Plume Interactions, and Space Radiation Design Considerations for All-Electric GEO Satellite Missions

The use of electric propulsion (EP) for geostationary Earth orbit (GEO) stationkeeping and geostationary transfer orbit offers satellite operators the opportunity to reduce mission costs and to increase revenue by enabling a higher dry mass to orbit compared with traditional chemical or EP systems. The penalty for such benefits comes, initially, in the form of an increased time-to-orbit whereby the low-thrust transfer orbit duration will range from a few months, at best, to possibly one year or more. During the low-thrust transfer, the spacecraft will experience prolonged exposure to the portions of the trapped radiation belts to which the GEO spacecraft otherwise would not be subjected-most notably the inner belt and slot region. Further, the spacecraft will also experience on the order of 105 h of high-density high-energy plume plasma-a more challenging operational environment compared with that typically applied to the GEO spacecraft. Applicable environments are introduced, an overview of specific operational effects is provided, and design guidelines are highlighted.

Initial results from Primary Arc effects on solar cells at LEO (PASCAL) flight experiment

Repeated low power, or primary arcing, may adversely affect the performance of space solar cells. The cumulative effects of primary arcing on common solar cell performance parameters has been the subject of numerous ground studies in simulated plasma environments. The Primary Arc effects on Solar Cells At LEO (PASCAL) flight experiment is presently active aboard in the International Space Station (ISS) and characterizing such effects in-orbit for numerous state-of-the-art space solar cells with initial results presented herein.

On-Orbit Total Dose Measurements From 1998 to 2007 Using pFET Dosimeters

An updated review of on-orbit measurements for multiple pFET dosimeters at GEO for 1998-2007 time period indicates excellent sensor performance over a range of dose rates and yields valuable information regarding space environment model (AE-8, AE-9, IGE-2006, and POLE)/transport tool validation.

On-Orbit Radiation Monitoring Using p-FET Dosimeter

Eight Lockheed Martin built telecommunications spacecraft operating at Geosynchronous Earth Orbit employ integrated spacecraft environmental monitoring systems which include dosimeters. Dosimeters were designed to provide measured on-orbit dose and dose rates for common spacecraft applications. The present study reviews sensor data during six years of in orbit operation as well as a notable Solar Cycle 23 space weather event. Results suggest favorable performance and illustrate the importance and the potential benefits of low mass, low power, low cost on-spacecraft dosimetry as a supplement to dedicated scientific data and space situational awareness. In orbit data assembled to date provides information that is useful in improving radiation modeling and prediction methods as well as radiation test methodology as related to realistic dose rates.

Geosynchronous ESD environment characterization via in situ measurements on host spacecraft

Controlling and mitigating spacecraft charging effects requires prudent design, test, and verification measures to related to material surface properties when exposed to a variety of operational and environmental conditions. In this paper we use two targeted sensors to characterize the surface charging environment and threat of surface / differential charging for June to October 2010. Surface potential measurements and ~4 keV to ~40 keV electron flux measurements are utilized to investigate the timescale of charging events, study complementary results amongst sensors on nearby spacecraft, and develop a process for near-real time charging threat assessment aboard host spacecraft. Findings are relevant for assessments of space system impacts resulting from surface discharges and ESD, simulations of surface charging, and laboratory testing of flight systems designs.

Surface Charging Considerations for Composite Materials Used in Spacecraft Applications

Graphite composites remain a preferred structural material for modern spacecraft applications despite the growing library of charging data on the surface charging properties of composites and resin. Additional ground test data obtained at a number of relevant temperatures and electron beam current densities extends the collective community knowledge on the charging properties of graphite composites in geostationary earth orbit environments. New data and analyses demonstrate that some common composite materials are susceptible to surface charging at the low current densities (<;100 nA/cm2) expected for lightly shielded or blanketed applications. Scaling results also demonstrate that electrostatic discharge transients occurring on graphite composite surface fail to follow familiar scaling laws.

Effects of Ion Energy on Single Event Effect Performance of LM139 and AD9042

High energy heavy ion testing of LM139 and AD9042 performed at NASA Space Radiation Laboratory offers new insight into device SEE response in the space environment.