Safe mode (spacecraft)
Encyclopedia
Safe mode is an operating mode of a modern spacecraft
during which all non-essential systems are shut down and only essential functions such as thermal management, radio reception and attitude control are active.
s penetrating spacecraft electrical systems can create false signals or commands and thus cause a trigger event. The central processor electronics are especially prone to such events.
for illumination of solar panels and for thermal management. The spacecraft then awaits for radio commands from its mission control center
monitoring for signals on its low-gain omnidirectional antenna
. Exactly what happens while in safe mode is dependent on the spacecraft design and its mission.
rocket firing at Saturn
of the Cassini spacecraft, where if a critical failure were to occur during this operation most if not all of the mission objectives would be lost anyway.
was on sol
451.
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
during which all non-essential systems are shut down and only essential functions such as thermal management, radio reception and attitude control are active.
Triggering events
Safe mode is entered automatically upon the detection of a predefined operating condition or event that may indicate loss of control or damage to the spacecraft. Usually the trigger event is a system failure or detection of operating conditions considered dangerously out of the normal range. Cosmic rayCosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
s penetrating spacecraft electrical systems can create false signals or commands and thus cause a trigger event. The central processor electronics are especially prone to such events.
Entry
The process of entering safe mode, sometimes referred to as safing, involves a number of immediate physical actions taken to prevent damage or complete loss. Power is removed from non-essential subsystems. Regaining attitude control, if lost, is the highest priority because it is necessary to maintain thermal balance and proper illumination of the solar panels. A tumbling or cartwheeling spacecraft can quickly roast, freeze or exhaust its battery power and be lost forever.In Safe Mode
While in this mode the preservation of the spacecraft is the highest priority. Typically all non-essential systems, such as science instruments, are shut down. The spacecraft attempts to maintain orientation with respect to the SunSun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
for illumination of solar panels and for thermal management. The spacecraft then awaits for radio commands from its mission control center
Mission Control Center
A mission control center is an entity that manages aerospace vehicle flights, usually from the point of lift-off until the landing or the end of the mission. A staff of flight controllers and other support personnel monitor all aspects of the mission using telemetry, and send commands to the...
monitoring for signals on its low-gain omnidirectional antenna
Omnidirectional antenna
In radio communication, an omnidirectional antenna is an antenna which radiates radio wave power uniformly in all directions in one plane, with the radiated power decreasing with elevation angle above or below the plane, dropping to zero on the antenna's axis. This radiation pattern is often...
. Exactly what happens while in safe mode is dependent on the spacecraft design and its mission.
Recovery
Recovery from safe mode involves reestablishing communication between the spacecraft and mission control, downloading any diagnostic data and sequencing power back on to the various subsystems to resume the mission. The recovery time can be anywhere from a few hours to days or weeks depending on the difficulty in reestablishing communications, conditions found on the spacecraft, distance to the spacecraft and the nature of the mission.Suppression
The spacecraft's ability to enter safe mode may be suppressed during periods of crucial spacecraft operations, such as during the orbit insertionOrbit insertion
Orbit insertion is the spaceflight operation of adjusting a spacecraft’s momentum to allow for entry into a stable orbit around a planet, moon, or other celestial body...
rocket firing at Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
of the Cassini spacecraft, where if a critical failure were to occur during this operation most if not all of the mission objectives would be lost anyway.
Manual entry
On occasion a spacecraft is placed in safe mode deliberately by mission control as the Spirit roverSpirit rover
Spirit, MER-A , is a robotic rover on Mars, active from 2004 to 2010. It was one of two rovers of NASA's ongoing Mars Exploration Rover Mission. It landed successfully on Mars at 04:35 Ground UTC on January 4, 2004, three weeks before its twin, Opportunity , landed on the other side of the planet...
was on sol
Timekeeping on Mars
Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars.Mars has an axial tilt and a rotation period similar to those of Earth. Thus it experiences seasons of spring, summer, autumn and winter much like Earth, and its...
451.
2009
- MROMars Reconnaissance OrbiterMars Reconnaissance Orbiter is a NASA multipurpose spacecraft designed to conduct reconnaissance and Exploration of Mars from orbit...
entered safe mode on August 26, 2009 for the second incident in a month, the fourth in 2009 and the eighth since launch in 2005. The spacecraft was kept in safe mode until December 8, 2009. - KeplerKepler MissionThe Kepler spacecraft is an American space observatory, the space-based portion of NASA's Kepler Mission to discover Earth-like planets orbiting other stars. The spacecraft is named in honor of the 17th-century German astronomer Johannes Kepler...
entered safe mode on June 15 and again on July 3, 2009. Both cases were triggered by an on-board processor reset. - Dawn entered safe mode due to a programming error during its February 17, 2009 MarsMarsMars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
flyby. - MESSENGERMESSENGERThe MErcury Surface, Space ENvironment, GEochemistry and Ranging space probe is a robotic NASA spacecraft in orbit around the planet Mercury. The spacecraft was launched aboard a Delta II rocket in August 2004 to study the chemical composition, geology, and magnetic field of Mercury...
entered safe mode during its third flyby of MercuryMercury (planet)Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
on September 29, 2009.
2007
- Cassini–Huygens download of the IapetusIapetusIapetus may mean:*Iapetus , a Titan in Greek mythology*Iapetus , one of the planet Saturn's moons*Iapetus Ocean, an ancient ocean between Laurentia and Baltica...
flyby data was interrupted by a safing event September 10, 2007. - New HorizonsNew HorizonsNew Horizons is a NASA robotic spacecraft mission currently en route to the dwarf planet Pluto. It is expected to be the first spacecraft to fly by and study Pluto and its moons, Charon, Nix, Hydra and S/2011 P 1. Its estimated arrival date at the Pluto-Charon system is July 14th, 2015...
entered safe mode March 19, 2007 due to an uncorrectable memory error in the primary Command and Data Handling (C&DH) computer. - Odyssey2001 Mars Odyssey2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectrometers and electronic imagers to hunt for evidence of past or...
has broken the communications link between the Mars rovers and EarthEarthEarth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
during several sudden safing events.
Incidents resulting in spacecraft loss or near loss
- Mars Global SurveyorMars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on 2...
entered safe mode and was lost when its batteries were overheated and destroyed by incorrect solar orientation on November 2, 2006. - SOHO entered safe mode and was nearly lost on June 25, 1998. Normal operations were eventually restored after a gap of four months.
- NEARNEAR ShoemakerThe Near Earth Asteroid Rendezvous - Shoemaker , renamed after its 1996 launch in honor of planetary scientist Eugene M. Shoemaker, was a robotic space probe designed by the Johns Hopkins University Applied Physics Laboratory for NASA to study the near-Earth asteroid Eros from close orbit over a...
entered safe mode, tumbled out of control and was nearly lost during the first attempt of Eros433 Eros433 Eros is a near-Earth asteroid discovered in 1898, and the first asteroid to be orbited by a probe . It is an S-type asteroid approximately 34.4×11.2×11.2 km in size, the second-largest NEA after 1036 Ganymed, and belongs to the Amor group.Eros is a Mars-crosser asteroid, the first known...
orbit insertionOrbit insertionOrbit insertion is the spaceflight operation of adjusting a spacecraft’s momentum to allow for entry into a stable orbit around a planet, moon, or other celestial body...
on December 20, 1998.