SERVIS: Space Environment Reliability Verification Integrated System

1. INTRODUCTION

The Space Environment Reliability Verification Integrated System (SERVIS) is being developed by the Institute for Unmanned Space Experiment Free Flyer (USEF) under the contract with the New Energy and Industrial Technology Development Organization (NEDO). The purpose of the project is to establish a parts database, a parts evaluation guideline and an equipment design guideline to utilize commercial-off-the-shelf parts and technologies (COTS) under the space environment so that they can be utilized for space applications. The SERVIS project has started in 1999 and will continue until 2011. During this period, two verification satellites were to be developed. The first satellite was already launched in October, 2003 and its two year on-orbit operation was successfully completed. The second satellite is now ready for launch.    This project has been established in order to strengthen technical and cost competitiveness of the Japanese space industry in the world market for the coming decade. In realizing this, the following considerations are taken into account. Cost reduction of satellites and their equipment is an urgent issue. In order to realize this, introduction of COTS is necessary. For realistic COTS application, low earth orbit (LEO) has been selected due to its reasonable radiation environment. And the orbit altitude for the verification satellites is selected about 1000 km. In order to reduce total cost, programmatic cost reduction in addition to hardware cost is also important. By achieving the above, it is expected to increase technical and cost competitiveness for LEO satellite buses and their equipment.   The entire project activity is comprised of four segments. They are; Ground evaluation tests for various COTS, including radiation tolerance test, Development and space verification of advanced experimental equipment with COTS, Development of two space verification satellites, SERVIS-1 and -2, Development of design infrastructure called "Virtual Integration."

2. Summary of SERVIS Satellites

The SERVIS satellite system summary is shown in Table 1. As payload, experimental equipment shown in Table 2 and 3 are onboard. Commercial Parts Test Unit (CPT) is also onboard in order to evaluate COTS parts performance precisely under on-orbit condition as shown in Table 4

Table 1 System Summary of Two Verification Satellites

Item SERVIS-1 SERVIS-2 Launch Date Oct. 30, 2003 June 2010(target) Launch Vehicle ROCKOT ROCKOT Operational Orbit 1000 km 1200 km i= 99.5 deg. SSO i= 100.4 deg. SSO Mission Duration 2 years 1 year Satellite Mass 840 kg 740 kg Dimensions 2.5 m(H) x 10.2 m(L) Generated Power more than 1300 W Satellite Control Centralized Control by Integrated Satellite Controller Attitude Control 3-axis Stabilization Power Supply 50 V Floating Bus System Data Handling CCSDS Recommended Space Packet Protocol Communications Telemetry: USB(2 kbps), HSB(256 kbps) Command: 4 kbps Propulsion Mono Propellant Hydrazine System, Thruster: 1N Satellite Operation USEF Space Operations Center (USOC) Ground Stations JAXA Ground Network Stations Resources for Payload Mass: >300 kg, Power: >500 W, Date Rate: >2400 bps

Table 2 Experimental Equipment onboard of SERVIS-1

Equipment Acronym Vane-type Propellant Tank System VTS Integrated Navigation Unit INU Power Control & Distribution Unit PCDS Advanced Paddle Drive Mechanism APDM Advanced TT & C Transponder ATTC On Board Computer OBC Integrated Satellite Controller with Star Sensor SIS Lithium Ion (Co type) Battery System LIB Fiber Optic Gyro Inertial Reference Unit FOIRU

Table 3 Experimental Equipment onboard of SERVIS-2

Equipment Acronym Lithium Ion (Mn type) Battery System with Automotive Technology LIBA High Assurance Data Management System ADMS Fault Tolerant Computer with CRAFT System CRAFT Plug-and-Play Remote Terminal Unit PPRTU High Performance Data Compressor HPDC Advanced Positioning Experimental Module APE Advanced Satellite Structure Experimental Module ASM Magnetic Bearing Wheel MBW RF-MEMS Experiment Unit MEMS

Table 4 COTS evaluated by Commercial Parts Test Unit

SERVIS-1 SERVIS-2 SRAM 1Mbit, 4Mbit 4Mbit, 8Mbit DRAM 128Mbit,256Mbit 256Mbit,512Mbit SOI SRAM 256kbit0.35 µm rule 128kbit0.18 µm rule FlashMemory NOR type 32Mbit NOR type 128Mbit FPGA SRAM type,EEPROM type SRAM type,EEPROM type

3. SERVIS-1 Space Verification Results

SERVIS-1, which was an 840kg weight box type satellite with COTS payloads, was launched on October 30, 2003 aboard ROCKOT from Plesetsk Cosmodrome in Russia. SERVIS-1 was operated exactly for two years after the launch. During that period, all experimental payloads had been operated normally and all of them well cleared "extra success level" criteria of the verification test which was established prior to the launch. Table 5 shows the frequency of single event upsets (SEUs) observed for COTS components in orbit, in comparison with predicted frequency as a result of ground radiation tolerance test. As shown in the table, actual frequency of SEUs observed on orbit was less than predicted frequency using ground test results. The table also indicates that better match between ground test and orbit result is observed for proton than for heavy ion, thus proving the concept that proton has the dominant effect for SEU for low earth orbit. Figure 1 shows examples of the proton and electron data measured by the Energetic Light Particle Spectrometer, which are plotted on a world map.

Table 5 Frequencies of Single Event Upsets (SEU) on COTS in SERVIS-1 Experimental Equipment and CPT

Equipment Part's Type SEU(times) Predicted values from heavy ion irradiation test Measured values on orbit OBC 32bit CPU 4.2 / day 0.16 / day 64M SDRAM 18 /day 0.005 / day 4M SRAM 18 /day 3.7 / day SIS 32bit CPU 0.23 / day 0.08 / day 1M EEPROM 0 / day 0 / day 256M SDRAM 4.5 / day 0.3/ day ATTC 16bit DAC 0.8 / day 0.06 / day 16bit ADC 1.0 / day 0.12 / day PCDS 16bit CPU 2.3* / year 1.5 / year CPT 1M SRAM 1.0 or 2.1* / day 0.79 / day 4M SRAM 3.4 or 6.6* / day 2.0 / day 128M SDRAM 2.6 or 0.2* / day 0.17 / day 256M SDRAM 3.6 or 0.5* / day 0.3 / day

*:Predicted values from proton irradiation ground test results

Figure 1 Proton and Electron data measured by SERVIS-1 Energetic Light Particle Spectrometer

4. TECHNICAL KNOWLEDGE BASES 4.1 Basic Concept    Technical knowledge bases are the ultimate product of SERVIS project. They are a group of documents to indicate the way to use COTS parts for space application through extensive ground evaluation test and orbit verification test. Those documents are now being assembled and updated, and will be finally completed after the SERVIS-2 on-orbit verification test is completed. 4.2 COTS Database    The Commercial Off-the-Shelf parts and technologies database (COTS Database) contains the result of ground evaluation tests especially that of radiation tolerance test.    By this database, one can learn to what extent a certain COTS part can withstand to the space environment, thus to give the criteria in using that particular COTS for space application.    Considering the criticality of COTS information to be used for space application, the database has two-tier structure. Namely, the first tier contains limited information open to the public, while the second tier has more detailed and specific information.  The first tier database contains following information.    1)  COTS ID number (assigned by USEF)    2)  General specification    3)  Summary of radiation test    4)  Summary of quality conformance test Click here for the first database Second tier and detailed database is restricted to the relevant personnel only and contains following information.    1)  Parts number    2)  Name of manufacturer    3)  Specification    4)  Screening test condition and its result    5)  Radiation test condition and its result    6)  Quality conformance test and its result    In case a potential user is interested in certain COTS parts by reviewing the first tier database, he can contact USEF for more detailed information and would be able to contact with the parts manufacturer for detailed discussion. 4.3 Parts Evaluation Guideline    This guideline specifies test and evaluation method and criteria for COTS components in order to apply them for space purposes. It contains following items. - Characterization of COTS components v.s. conventional hi-rel parts in general, and explain issues and necessary considerations of COTS's usage for space application. - Define ground tolerance test methods and criteria for space application - Estimation method of accurate radiation environment at actual COTS location in the satellite equipment. 4.4 Equipment Design Guideline    This guideline indicates various considerations which are required for engineers in order to use COTS parts and technologies for space equipment. It is intended that by following this guideline, space equipment with COTS would have sufficient quality and reliability performances for space use.    The guideline consists of two parts. Part I elaborates design criteria and necessary considerations to be followed. It is intended it will serve as a design handbook which a design engineer always keeps on his desk for daily work. Part II explains example of SERVIS-1 experimental equipment from the standpoint how COTS parts and technologies were applied in those 9 equipment. It is intended to promote the understanding of COTS application for space usage.

(c)Institute for Unmanned Space Experiment Free Flyer(USEF)