Space Environmental Hazards Effects of Space Weather Meidad Pariente
Space Environment Effects on Satellites – Short Brief• The environment in space has significant effect on satellites. The discussion below highlights the principal effects experienced by satellites. • Satellite Charging/ Deep Charging • Satellite Discharging • Hardware damage • Electric problems
Satellite Charging• Satellite charging is a variation in the electrostatic potential of a satellite with respect to the surrounding low density plasma around the satellite or to another part of the satellite.• The extent of the charging depends on both design and orbit.• The two primary mechanisms
Deep Charging• Deep charging of a satellite occurs when cosmic ray particles pass through a satellite and ionize atoms within, through collisions.• Some of these particles are solar in origin, but the majority are galactic and with no preference to time or light conditions.• They do show some dependence on
Satellite Discharging• The satellites most vulnerable to charging/discharging are those located at geosynchronous altitude. Discharges as high as 20,000 volts (V) have been experienced.• Satellites in geosynchronous orbits typically move both in and out of the upper regions of the Van Allen Radiation Belts and the Earths
Hardware Damage• Sudden electrostatic discharge (high current or arc) can cause hardware damage, such as: • Blown fuses or exploded transistors, capacitors and other electronic components • Vaporized metal parts • Structural damage • Breakdown of thermal coatings
Electric Problems• These discharges can result in electrical or electronic problems, such as: • False commands • On/Off circuit switching • Memory changes • Solar cell degradation • Degradation of optical sensors
Particle Collision• High energy solar flare particles and galactic cosmic rays can cause direct damage to the surface of a satellite. The damage can include vaporization of surface materials and structural damage. These particles can also enter star or horizon sensors and mimic reference points.
Space Environmental Hazards Anomalies Space Weather
Sun Index• Two of the most used space weather index are • Smoothed Sunspot Number (SSN) Geomagnetic Planetary Geomagnetic „Acrivity‟ • Solar „Acrivity‟ K Index (Kp) or SSNA Index (Ap)Level Kp Ap Level >250 Extreme 7-9 >100 Severe Storm 150-250 Very High 6 50-99 Major Storm 80-150 High 5 30-49 Minor Storm 40-80 Moderate 4 16-29 Active 20-40 Low 3 8-15 Unsettled 0-20 Very Low 0-2 0-7 Quiet
Geomagnetic Disturbances• The disturbance of the geomagnetic field may be measured by an a magnetometer.• Several magnetometer data from dozens of observatories in one minute intervals are potentially available.• The data is tracked in „real-time‟ and allows to monitor the current state of the geomagnetic conditions.
Kp and NOAA G-scale Kp Index NOAA Space Weather Scale Geomagnetic Storm Level Kp <= 4 G0 Kp = 5 G1 Kp = 6 G2 Kp = 7 G3 Kp = storm Weather Prediction CenterKp of 0 to 4 is below 8 NOAA Space G4
NOAA Space Weather Scale for Geomangetic Storm Physic AverageSc Descri al Frequency Effect to Spacecraft Operationsale ptor Measur (1 cycle = 11 e years) may experience extensive surface 4 per cycle ExtremG5 charging, problems with orientation, Kp=9 (4 days per e uplink/downlink and tracking satellites. cycle) may experience surface charging and 100 per cycleG4 Severe tracking problems, corrections may be Kp=8 (60 days per needed for orientation problems cycle) surface charging may occur on satellite components, drag may 200 per cycleG3 Strong increase on low-Earth-orbit satellites, Kp=7 (130 days per and corrections may be needed for cycle) orientation problems. corrective actions to orientation may
NOAA Space Weather Scale for Solar Radiation Storm AverageSc Descr Physical Frequency Effect to Spacecraft Operationsale iptor Measure (1 cycle = 11 years) Flux Number of Level of storm events >=10Me when Kp level Solar Radiation Storm V was met; particles (number of (ions) storm days) satellites may be rendered useless, memory impacts can cause loss of control, may cause Extre Fewer than 1S5 serious noise in image data, star-trackers may 105 me per cycle be unable to locate sources; permanent damage to solar panels possible. may experience memory device problems and noise on imaging systems; star-tracker 3 per cycleS4 Severe 104 problems may cause orientation problems, and solar panel efficiency can be degraded
Geomagnetic Activity vsNumber of Recorded Anomalies (April 2010)
Space Environmental Hazards The Systems Engineer POV
Designing a Robust satellite – Good Engineering Practice• Environmental Testing is not enough !• Glitches, Faulty hardware and computer mishaps due to environmental conditions must be considered and anticipated.• Satellites should be fully automatic for as long as possible (no less than 48 hours)
Designing a Robust satellite – Tips and Tricks• Check, check and than double check your system logic for dead ends.• If you have such a single point failure it will surly occur, hence protect the satellites with timeouts• Whenever possible perform sanity checks, especially regarding crucial data• Critical system parameters should
Hardware Protection• Exterior surface of satellite is exposed to charging and overcharging, especially when using ion thrusters, hence protection measured should be implemented on the outer surface as well• Listen to weather reports ! When a storm is approaching shut down all redundant units, and keep only
The Galaxy-15 Case Study• 5/4/2010 – Contact with Galaxy-15 Lost • Galaxy-15 team was unable to switch the payload off, hence causing interference to other satellites, enforcing evasive maneuvers and exposed to claims.• 23/10/2010 – Satellite reboot after battery drain • Satellite enters safe mode after six months of eastward drift• Currently – at 121ºW (originally 133ºW and drifted until 93ºW) used as a relay station for GPS signals
Conclusions• Anomaly trend proved to be correlated with geomagnetic activity.• Most of current satellite designs proved to be resilient to experienced geomagnetic activity.• Still catastophric events happen during peak events.• Galaxy 15 events to be investigated to carefully verify repeatabilty.