微小卫星数据存储器单粒子作用的检测及纠错

因为辐射导致的单粒子翻转效应（SEU）,使得微小卫星星上存储器在太空运行时其内容可能出现小概率错误,这种错误会影响计算机系统的运行和关键数据。文章阐述了“清华一号”微小卫星数据处理系统对SEU的纠错方法,分别介绍了实现（12,8）和（39,32）的汉明码纠错设计和基于FPGA的三模块冗余纠错编码方法,并分析了这些方法的工作原理和过程。     

Single-event upset in geostationary transfer orbit during solar-activity maximum period measured by the Tsubasa satellite

This paper reports single-event upset (SEU) occurrence related to the space radiation environment in geostationary transfer orbit during solar-activity maximum period measured by the Tsubasa satellite. Most SEUs are measured in the inner radiation belt, indicating that they are mainly caused by trapped protons. Thus, the spatial distribution and the temporal variation of the SEU count correlate well with those of trapped protons. The peak SEU rate appears around L = 1.4. The transition point from SEUs caused by trapped protons to those caused by galactic cosmic rays is around L = 2.6. During the experiment period, increased SEU count was sometimes detected due to solar and geomagnetic events outside the inner radiation belt.     

高能重离子径迹结构对单粒子翻转的影响

利用解析法计算了高能重离子的径迹结构,通过MonteCarlo方法研究了径迹结构对微电子芯片单粒子翻转的影响.结果表明,考虑了径迹结构的影响后,当离子能量较高时,具有小尺寸灵敏单元、低翻转阈值的芯片的翻转截面较传统的LET描述结果小许多;当离子更重时,这种差别对灵敏单元尺寸较大、翻转阈值较高的芯片也变得较明显.即离子径迹结构的影响是通过其有效地沉积到灵敏单元中的能量与翻转阈值相比较而表现出来的.还研究了作用距离较深、结构宽大的径迹造成的相邻多个灵敏单元的同时翻转,即多位翻转现象,这是用LET所不能反映的.      

In orbit performance of butane propulsion system

The present work focuses on the determination of the in orbit performance of the Alsat-1 microsatellite propulsion system. The satellite mass is 90 kg, of which 6.2 kg is the propulsion system dry mass. The system is a butane propulsion system using low power resistojet thruster with 2.3 kg of propellant. The liquefied butane gas was selected due to its higher storage density and safety compared to the other propellants used for microsatellites. The purpose of this paper is the analysis of the firings performed after the launch of the satellite and to evaluate the system specific impulse and thrust level during the system lifetime. A total of 273 firings were performed on the Alsat-1 propulsion system in the period between the end of 2002 and mid 2009, the cumulated firing time is more than 12 h 49 min. The analysis of all the propulsion telemetry data shows that the system provides a total mission delta V of 25.3 m/s which is more than the 10 m/s specified for this mission. Furthermore, the mission average specific impulse and thrust are respectively 99.9 s and 48.8 mN.     

Microelectronics effects as seen on CRRES.

A MicroElectronics Test Package (MEP) measured total dose degradation and single event upsets (SEUs) on 60 device types on the Combined Release and Radiation Effects Satellite (CRRES) in an 18 degrees inclination orbit between 350 km and 36000 km from July 1990 to October 1991. Simultaneous measurements of the high energy particle environment were used to make a direct cause and effect comparison of the energetic particle backgrounds and microelectronic performance characteristics. The galactic cosmic ray background for the period of the CRRES mission was at a minimum. The SEUs experienced from the cosmic ray background were correspondingly few in number, but surprisingly produced an equal probability of upset over an L-shell range of 8.5 Earth radii (RE) down to less than 3.0 RE. Cosmic ray induced upset frequencies in proton sensitive chips were over 2 orders of magnitude lower than those produced by protons in the heart of the inner proton radiation belts. Multiple upsets, those produced when a single particle upsets more than one memory location, were just as common from protons as from cosmic rays.     

影响卫星故障的空间天气分析

基于美国国家地球物理数据中心(NGDC) 2384例和中国19颗卫星的263例卫星故障信息, 结合1963-2012年小时平均的多种空间环境数据, 定量分析了三种卫星故障发生期间的空间要素特征, 探讨单粒子锁定(SEU)、表面充电致静电放电(ESD)和内部深层充电所致电子引起的电磁脉冲(ECEMP)与空间天气事件的可能联系, 得出以下主要结论. (1)大部分SEU和ECEMP发生于空间天气平静时, 但在其前后3日内地磁活动达到了磁暴水平, 相对来说比例最大的发生在Dst_min之后第3日 (48～72h). (2) ESD受地磁活动和高能电子通量影响明显. 与磁暴、相对论电子通量增强事件的季节性相对应, 两分点附近ESD和ECEMP的发生率高; 93.6% 的 ESD发生前后72h内地磁活动达到磁暴水平, 故障发生时间均匀分布在 Dst_min前0～48h 和后0～24h; 54.9%的ESD 发生时处于地磁暴期(Dst <-30nT), 以-50～-30nT的小磁暴水平居多; 40.6%的ESD发生于高能电子通量高水平期(≥ 103pfu, 1pfu =1cm-2·s-1·sr-1), 81.9%的ESD发生前后72h 内高能电子通量峰值≥ 103pfu, 发生率最高时段为电子通量峰值前 48～72h. (3)高能电子对中国同步轨道卫星的SEU影响明显, 42.5% 故障发生 时高能电子通量≥ 103pfu, 故障在峰值前48～72h和峰值后48～72h 的发生概率相当, 约为23.0%. (4)同步轨道卫星SEU受太阳质子事件的影响相对较大, 22.5%的中国同步轨道卫星故障发生前后72h内发生了太阳质子事件, 季节性不明显.      

几种256Kbit SRAM芯片的单粒子翻转规律

给出了实践４号（ＳＪ－４）星载ＩＤＴ７１２５６Ｄ高速ＣＭＯＳ静态存储器和ＨＭ８８３２异步静态存储器单粒子事件（ＳＥＵ）的总翻转率,器件类型翻转率,逻辑状态翻转率,并与国外某些卫星的监测结果进行了比较。另外对部分ＳＥＵ数据进行了统计分析,给出了ＳＥＵ的片上地址和到达时间差的分布规律及拟合曲线。     

A comparison of two different types of geosynchronous satellite measurements during the 1989 solar proton events.

The proton telescope aboard the GOES-7 satellite continuously records the proton flux at geosynchronous orbit, and therefore provides a direct measurement of the energetic protons arriving during solar energetic particle (SEP) events. Microelectronic devices are susceptible to single event upset (SEU) caused by both energetic protons and galactic cosmic ray (GCR) ions. Some devices are so sensitive that their upsets can be used as a dosimetric indicator of a high fluence of particles. The 93L422 1K SRAM is one such device. Eight of them are on the TDRS-1 satellite in geosynchronous orbit, and collectively they had been experiencing 1-2 upset/day due to the GCR background. During the large SEP events of 1989 the upset rate increased dramatically, up to about 250 for the week of 19 Oct, due to the arrival of the SEP protons. Using the GOES proton spectra, the proton-induced SEU cross section curve for the 93L422 and the shielding distribution around the 93L422, the calculated upsets based on the GOES satellite data compared well against the log of measured upsets on TDRS-1.     

The contribution of local gravimetric geoid models to the calibration of satellite altimetry data and an outlook of the latest GOCE GGM performance in Gavdos

The use of geoid heights has been one of the available methodologies utilized for the independent calibration/validation of altimeters on-board satellites. This methodology has been employed for long in the Gavdos dedicated cal/val facility (Crete, Greece), where calibration results for the Jason satellites have been estimated, both for ascending and descending passes. The present work gives a detailed overview of the methodology followed in order to estimate a high-resolution and accuracy gravimetric geoid model for the wider Gavdos area, in support of the on-going calibration work. To estimate the geoid model, the well-known remove-compute-restore method is used while residual geoid heights are estimated through least-squares collocation so that associated errors are determined as well. It is found that the estimated formal geoid errors from LSC along passes 018 and 109 of Jason satellites, used for the bias estimation, range between ±0.8–1.6 cm. The so-derived geoid heights are employed in the determination of the Jason-2 altimeter bias for all available cycles (cycles 1-114, spanning the period from July 2008 to August 2011) together with the RioMed DOT model. From the results acquired the Jason-2 bias has been estimated to be +196.1 ± 3.2 mm for pass 109 and +161.9 ± 5.1 mm for pass 018. Within the same frame, the GOCE/GRACE-based geopotential model GOCO02s has been used to estimate the mean dynamic ocean topography and the steady-state circulation in the area around Gavdos. The so-derived DOT model was used to estimate the Jason-2 bias in an effort to evaluate the performance of satellite-only geoid models and investigate whether their spatial resolution and accuracy provides some improvement w.r.t. traditional local gravimetric geoids. From the results acquired with geoid heights from GOCO02s, the estimated Jason-2 bias deviates significantly from that of the local gravimetric model, which can be attributed to a possible mean offset and the low resolution of GOCE-based GGMs. On the other hand, when the newly estimated GOCE-based DOT was employed with geoid heights from the local gravimetric geoid model, the Jason-2 bias has been estimated to be +185.1 ± 3.2 mm for pass 109 and +130.2 ± 5.1 mm for pass 018.     

美国几架航天飞机所发生的SEU研究

本文对1991年美国发射的5架不同倾角不同高度的低地球轨道航天飞机所遇到的单粒子翻转事件进行了考查和研究．结果证实在极光区和南大西洋异常区仍可能发生大量单粒子事件,大大地影响到航天器的安全,对此文中给出了一些结论和建议．     

Kalman filtering for GPS/magnetometer integrated navigation system

This paper investigated the data processing method for a GPS/IMU/magnetometer integrated system with Kalman filtering (KF). As a result of GPS/IMU/magnetometer land vehicle system, dead-reckoning of magnetometer and accelerometer integrated subsystem bridged very well the GPS signal outage due to the trees on the two sides of the road. Both differential GPS data processing method and the carrier-phase method with magnetometers’ outputs for predicting the car position, velocity, and acceleration (PVA) are presented. The results from DGPS with Kinematical Positioning (KINPOS) software shown that the averages of the north, east, and down direction standard deviation (short for “std”) are 0.014, 0.010, and 0.018 m, respectively. The std of velocities and accelerations derived by the position and velocity differentiation are 10, 7, 13 mm/s, 7, 5, 9 mm/s², respectively. This method for getting velocities and accelerations requires higher accurate position coordinates. But the position accuracy has frequently been degraded in this case when the car drove under the trees or other similar kinematical environments. That caused the larger velocity and acceleration errors. While the results from the carrier-phase method are std of the velocities = 2.1 mm/s, 1.3 mm/s, 3.7 mm/s in north, east, down, and std of the accelerations = 1.5 mm/s², 0.9 mm/s², 2.3 mm/s² for the static test period; as compared with KINPOS software results, std of the velocity difference between the carrier-phase method and the DGPS method = 7 mm/s, 6.9 mm/s, 9.7 mm/s in north, east, down direction, and std of acceleration difference = 5.0 mm/s², 4.5 mm/s², 7.5 mm/s² in north, east, down direction for the kinematical test period. Obviously, errors come from both the carrier-phase method and DGPS velocity and acceleration results derived directly by the position differentiation. In addition, better accuracy of positions than that before KF has been got by means of velocities and accelerations derived by the carrier-phase method after KF.     

质子引发的单粒子翻转率估算的研究

根据质子单粒子翻转事件的物理本质,及空间高能质子环境特性,给出了一种基于重离子单粒子翻转实验数据基础之上的估算质子引发的单粒子翻转的方法.利用这种方法计算了几种器件的翻转情况,与地面模拟实验及飞行观测结果符合得非常好.      

Tolerance of chufa (Cyperus esculentus L.) plants,representing the higher plant compartment in bioregenerative life support systems,to super-optimal air temperatures

Plants intended to be included in the photosynthesizing compartment of the bioregenerative life support system (BLSS) need to be studied in terms of both their production parameters under optimal conditions and their tolerance to stress factors that might be caused by emergency situations. The purpose of this study was to investigate tolerance of chufa (Cyperus esculentus L.) plants to the super-optimal air temperature of 45 ± 1 °C as dependent upon PAR (photosynthetically active radiation) intensity and the duration of the exposure to the stress factor. Chufa plants were grown hydroponically, on expanded clay, under artificial light. The nutrient solution was Knop’s mineral medium. Until the plants were 30 days old, they had been grown at 690 μmol m⁻² s⁻¹ PAR and air temperature 25 °C. Thirty-day-old plants were exposed to the temperature 45 °C for 6 h, 20 h, and 44 h at PAR intensities 690 μmol m⁻² s⁻¹ and 1150 μmol m⁻² s⁻¹. The exposure to the damaging air temperature for 44 h at 690 μmol m⁻² s⁻¹ PAR caused irreversible damage to PSA, resulting in leaf mortality. In chufa plants exposed to heat shock treatment at 690 μmol m⁻² s⁻¹ PAR for 6 h and 20 h, respiration exceeded photosynthesis, and CO₂ release in the light was recorded. Functional activity of photosynthetic apparatus, estimated from parameters of pulse-modulated chlorophyll fluorescence in Photosystem 2 (PS 2), decreased 40% to 50%. After the exposure to the stress factor was finished, functional activity of PSA recovered its initial values, and apparent photosynthesis (P_apparent) rate after a 20-h exposure to the stress factor was 2.6 times lower than before the elevation of the temperature. During the first hours of plant exposure to the temperature 45 °C at 1150 μmol m⁻² s⁻¹ PAR, respiration rate was higher than photosynthesis rate, but after 3–4 h of the exposure, photosynthetic processes exceeded oxidative ones and CO₂ absorption in the light was recorded. At the end of the 6-h exposure, P_apparent rate was close to that recorded prior to the exposure, and no significant changes were observed in the functional activity of PSA. At the end of the 20-h exposure, P_apparent rate was close to its initial value, but certain parameters of the functional activity of PSA decreased 25% vs. their initial values. During the repair period, the parameters of external gas exchange recovered their initial values, and parameters of pulse-modulated chlorophyll fluorescence were 20–30% higher than their initial values. Thus, exposure of chufa plants to the damaging temperature of the air for 20 h did not cause any irreversible damage to the photosynthetic apparatus of plants at either 690 μmol m⁻² s⁻¹ or 1150 μmol m⁻² s⁻¹ PAR, and higher PAR intensity during the heat shock treatment enhanced heat tolerance of the plants.     

Status of the T2L2/Jason2 Experiment

The T2L2 (Time Transfer by Laser Link) project, developed by CNES and OCA will permit the synchronization of remote ultra stable clocks and the determination of their performances over intercontinental distances. The principle of the experiment derives from Satellite Laser Ranging (SLR) technology with dedicated space equipment. T2L2 was accepted in 2005 to be on board the Jason2 altimetry satellite. The payload consists of both event timer and photo detection modules. The system uses the ultra-stable quartz oscillator of DORIS as on-board reference clock on one hand, and the Laser Reflector Array, making T2L2 a real two-way time transfer system on the other hand. The expected time stability of the T2L2 instrument (detection and timing), referenced by the DORIS oscillator and including all internal error sources should be at the level of 10–12 ps at 1 s and <1 ps at 1000 s. The metrological specifications of T2L2 should permit to maintain a precision of 1 to a few ps when measuring the phase of a clock during around 1000 seconds.     

小卫星设计中软件重注入的关键技术研究

针对小卫星的一体化设计思想，采用CCSDS测控体制，星上采用CAN总线的分布网络，对小卫星软件重注入的课题做了深入的研究。     

80C31单粒子效应敏感度评估

采用串列静电加速器对同步轨道气象卫星扫描辐射计控制器用８０Ｃ３１微控制器进行了单粒子效应模拟试验，得到了器件的错误截面与ＬＥＴ关系曲线；根据试验结果，对器件在同步轨道重离子环境中的翻转率进行了预计。     

Evidence for the lowering of the centroid of daytime thermospheric O(D) 630.0 nm emission over the magnetic equator: First results

It is shown in this paper for the first time that the intensity of the daytime thermospheric O(¹D) 630.0 nm airglow as measured by the ground-based dayglow photometer over Trivandrum (8.5°N; 77°E; dip lat. 0.5°N), a geomagnetic dip equatorial station, exhibit a direct correlation with the electron density at 180 km. This altitude is about ∼40 km lower than the believed centroid of the O(¹D) 630.0 nm dayglow emission i.e. 220 km. This observation is contrary to the understanding of the behavior of O(¹D) 630.0 nm dayglow over equatorial/low latitudes. Over these latitudes, the variations of the measured intensity of O(¹D) 630.0 nm dayglow are known to be associated with the changes in the electron density at altitudes around 220 km, the centroid of this emission. In this context, the present results indicating the lowering of the peak altitude of O(¹D) 630.0 nm emission from ∼220 to ∼180 km over the dip equator is new. Recent results on solar XUV flux indicate that this could be an important parameter that controls the O(¹D) 630.0 nm dayglow excitation rates through modulations in the neutral and ionic composition in lower thermosphere-ionosphere region. However, the lowering of the centroid of O(¹D) 630.0 nm emission, as shown in this study, has been ascribed primarily to the fountain effect associated with the equatorial ionization anomaly.     

Passepartout Sherpa – A low-cost,reusable transportation system into the stratosphere for small experiments

The Passepartout sounding balloon transportation system for low-mass (<$<$1200 g) experiments or hardware for validation to an altitude of 35 km is described. We present the general flight configuration, set-up of the flight control system, environmental and position sensors, power system, buoyancy considerations as well as the ground control infrastructure including recovery operations. In the telemetry and command module the integrated airborne computer is able to control the experiment, transmit telemetry and environmental data and allows for a duplex communication to a control centre for tele-commanding. The experiment module is mounted below the telemetry and command module and can either work as a standalone system or be controlled by the airborne computer. This spacing between experiment- and control unit allows for a high flexibility in the experiment design. After a parachute landing, the on-board satellite based recovery subsystems allow for a rapid tracking and recovery of the telemetry and command module and the experiment. We discuss flight data and lessons learned from two representative flights with research payloads.