MEO: Environments

Sporadic Environment | Shower Environment | Lunar Environment

Shower Meteoroid Environment

The Earth, and spacecraft near it, encounters quasi-periodic meteoritic enhancements caused by streams of material ejected from mainly short period comets that pass near the Earth’s orbit. These streams of debris produce meteor showers observed here on Earth, and normally represent only a modest enhancement over the background (a few percent). The density of material in a stream, however, can be increased by a recent entry of the parent comet into the inner Solar System, thereby resulting in an enhanced shower (meteor rates of several hundred per hour) or a meteor storm (rates in excess of 1000 meteors per hour). As might be expected, an enhanced shower or storm presents a time of increased risk for spacecraft. Mitigating the meteoroid risks from such events can be accomplished by operational procedures, such as reorienting a vehicle to point sensitive equipment away from the radiant, slewing solar panels edge-on to minimize the cross sectional area presented, and closing shutters to protect sensitive optics.

The Meteoroid Environment Office (MEO) has developed the MSFC Meteoroid Stream Model to forecast meteor showers for Earth and Earth orbiting spacecraft.

MSFC Meteoroid Stream Model
The MSFC Meteoroid Stream Model simulates particle ejection and subsequent evolution from comets in order to provide meteor shower forecasts to spacecraft operators for hazard mitigation and mission planning purposes. Custom forecasts are available from the MEO by request.

A 15th order RADAU integrator is used to integrate meteoroid position and velocity forward in time, accounting for the effects of radiation pressure, Poynting-Robertson drag, and the gravitational forces of the planets. General relativistic effects have also been taken into account. The number of particles simulated depends on the particular comet in question. See Moser & Cooke (2004) and Moser & Cooke (2008) for more details.

Meteor Shower History
Streams that are notorious for producing enhanced showers or storms at Earth are the Perseids, the Draconids (also called the Giacobinids) and the Leonids. The Leonids are especially famous for producing spectacular meteor storms at 33-year intervals. The table below presents information on those meteor streams that are known to have the potential for causing outbursts at Earth and the Earth-Sun L1 and L2 points.

At least one satellite has been damaged and one effectively killed by encounters with meteor streams. In mid-September of 1967, the Mariner IV spacecraft was located midway between the orbits of Earth and Mars when it encountered an unknown meteor stream. The onboard meteor counter registered a thousand-fold increase in flux for about 45 minutes, during which time the spacecraft was slightly torqued about its roll axis and had some of its thermal insulation ripped away. Mariner IV was lucky in that it suffered no major damage; this was not the case for Olympus, a European communications satellite. During an enhanced shower in August of 1993, Olympus was struck by a Perseid somewhere near its electronics bay. The resulting plasma discharge generated enough current to disable a gyro, causing the satellite to tumble. By the time control was restored some days later, the spacecraft had used practically all of its fuel and was effectively dead as far as its mission was concerned.