Communications blackout
Encyclopedia
In telecommunication
s, communications blackouts are
, which are also known as radio blackouts, ionization blackouts, or reentry blackouts, are caused by an envelope of ionized air around the craft, created by the heat from the compression of the atmosphere by the craft. The ionized air interferes with radio signals. For the Mercury
, Gemini
, and Apollo spacecraft, such communications blackouts lasted for several minutes. Gemini 2
, for example, endured such a blackout for four minutes, beginning at 9 minutes 5 seconds into the flight.
For Apollo missions, the communications blackout was approximately three minutes long. For Apollo 16
, for example, pre-advisory data (PAD) for re-entry listed the expected times for re-entry communications blackout to be from 0 minutes 16 seconds after entry interface to 3 minutes 33 seconds after entry interface (a total of 3 minutes 17 seconds). For the Apollo 13
mission, the blackout was much longer than normal because the flight path of the spacecraft was unexpectedly at a much shallower angle than normal. According to the mission log maintained by Gene Kranz
, the Apollo 13 re-entry blackout lasted around 6 minutes, beginning at 142:39 and ending at 142:45, and was 1 minute 27 seconds longer than had been predicted.
Communications blackouts for re-entry are not solely confined to entry into Earth's atmosphere. They apply to entry into any atmosphere where such ionization occurs around a craft. The Mars Pathfinder
endured a 30 second communications blackout as it entered Mars' atmosphere, for example. The Huygens probe
endured a communications blackout as it entered the atmosphere of Titan
.
Until the creation of the Tracking and Data Relay Satellite System
, the Space Shuttle
would, like Gemini, Mercury, Apollo, and others, endure a 30 minute long communications blackout before landing. However, the Shuttle can communicate with a Tracking and Data Relay Satellite
during re-entry. This is because the shape of the Shuttle creates a "hole" in the ionized air envelope, at the tail end of the craft, through which it can communicate upwards to a satellite in orbit and thence to a ground station.
are measured by the National Oceanic and Atmospheric Administration
on a scale that goes from 1 (minor) to 5 (extreme).
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
s, communications blackouts are
- a cessation of communicationsTelecommunicationTelecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
or communications capability, caused by a lack of powerElectric powerElectric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
to a communications facility or to communications equipment. - a total lack of radio communications capability, caused by ionosphericIonosphereThe ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
anomalies, e.g., during strong auroral activity or during re-entry of a spacecraftSpacecraftA 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....
into the Earth's atmosphere.
Reentry communications blackouts
The communications blackouts that affect spacecraft re-entering the Earth's atmosphereAtmospheric reentry
Atmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...
, which are also known as radio blackouts, ionization blackouts, or reentry blackouts, are caused by an envelope of ionized air around the craft, created by the heat from the compression of the atmosphere by the craft. The ionized air interferes with radio signals. For the Mercury
Project Mercury
In January 1960 NASA awarded Western Electric Company a contract for the Mercury tracking network. The value of the contract was over $33 million. Also in January, McDonnell delivered the first production-type Mercury spacecraft, less than a year after award of the formal contract. On February 12,...
, Gemini
Project Gemini
Project Gemini was the second human spaceflight program of NASA, the civilian space agency of the United States government. Project Gemini was conducted between projects Mercury and Apollo, with ten manned flights occurring in 1965 and 1966....
, and Apollo spacecraft, such communications blackouts lasted for several minutes. Gemini 2
Gemini 2
Gemini 2 was the second spaceflight of the American human spaceflight program Project Gemini. Gemini 2, like Gemini 1, was an unmanned mission intended as a test flight of the Gemini spacecraft. Unlike Gemini 1, which was placed into orbit, Gemini 2 made a suborbital flight, primarily intended to...
, for example, endured such a blackout for four minutes, beginning at 9 minutes 5 seconds into the flight.
For Apollo missions, the communications blackout was approximately three minutes long. For Apollo 16
Apollo 16
Young and Duke served as the backup crew for Apollo 13; Mattingly was slated to be the Apollo 13 command module pilot until being pulled from the mission due to his exposure to rubella through Duke.-Backup crew:...
, for example, pre-advisory data (PAD) for re-entry listed the expected times for re-entry communications blackout to be from 0 minutes 16 seconds after entry interface to 3 minutes 33 seconds after entry interface (a total of 3 minutes 17 seconds). For the Apollo 13
Apollo 13
Apollo 13 was the seventh manned mission in the American Apollo space program and the third intended to land on the Moon. The craft was launched on April 11, 1970, at 13:13 CST. The landing was aborted after an oxygen tank exploded two days later, crippling the service module upon which the Command...
mission, the blackout was much longer than normal because the flight path of the spacecraft was unexpectedly at a much shallower angle than normal. According to the mission log maintained by Gene Kranz
Eugene F. Kranz
Kranz's book, titled Failure Is Not an Option, published five years after the movie, stated, "...a creed that we all lived by: "Failure is not an option."" . The book has three index references for the phrase, but none of those give any indication of the phrase being apocryphal...
, the Apollo 13 re-entry blackout lasted around 6 minutes, beginning at 142:39 and ending at 142:45, and was 1 minute 27 seconds longer than had been predicted.
Communications blackouts for re-entry are not solely confined to entry into Earth's atmosphere. They apply to entry into any atmosphere where such ionization occurs around a craft. The Mars Pathfinder
Mars Pathfinder
Mars Pathfinder was an American spacecraft that landed a base station with roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight wheeled robotic rover named Sojourner.Launched on December 4, 1996 by NASA aboard a Delta II booster a...
endured a 30 second communications blackout as it entered Mars' atmosphere, for example. The Huygens probe
Huygens probe
The Huygens probe was an atmospheric entry probe carried to Saturn's moon Titan as part of the Cassini–Huygens mission. The probe was supplied by the European Space Agency and named after the Dutch 17th century astronomer Christiaan Huygens....
endured a communications blackout as it entered the atmosphere of Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....
.
Until the creation of the Tracking and Data Relay Satellite System
Tracking and Data Relay Satellite System
The Tracking and Data Relay Satellite System is a network of American communications satellites and ground stations used by NASA for space communications. The system was designed to replace an existing network of ground stations that had supported all of NASA's manned flight missions...
, the Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
would, like Gemini, Mercury, Apollo, and others, endure a 30 minute long communications blackout before landing. However, the Shuttle can communicate with a Tracking and Data Relay Satellite
Tracking and Data Relay Satellite
A Tracking and Data Relay Satellite is a type of communications satellite that forms part of the Tracking and Data Relay Satellite System used by NASA and other United States government agencies for communications to and from independent "User Platforms" such as satellites, balloons, aircraft,...
during re-entry. This is because the shape of the Shuttle creates a "hole" in the ionized air envelope, at the tail end of the craft, through which it can communicate upwards to a satellite in orbit and thence to a ground station.
Space weather communications blackouts
Radio blackouts caused by space weatherSpace weather
Space weather is the concept of changing environmental conditions in near-Earth space or thespace from the Sun's atmosphere to the Earth's atmosphere. It is distinct from the concept ofweather within the Earth's planetary atmosphere...
are measured by the National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
on a scale that goes from 1 (minor) to 5 (extreme).