A countdown is a sequence of backward counting to indicate the time remaining before an event is scheduled to occur. NASA commonly employs the terms "L-minus" and "T-minus" during the preparation for and anticipation of a rocket launch, and even "E-minus" for events that involve spacecraft that are already in space, where the "T" could stand for "Test" or "Time", and the "E" stands for "Encounter", as with a comet or some other space object, like a spacecraft .
37-459: Other events for which countdowns are commonly used include the detonation of an explosive, the start of a race, the start of the New Year , or any anxiously anticipated event. An early use of a countdown once signaled the start of a Cambridge University rowing race. One of the first known associations with rockets was in the 1929 German science fiction movie Frau im Mond (English: Woman in
74-975: A lunar calendar or a lunisolar calendar . Chinese New Year , the Islamic New Year , Tamil New Year ( Puthandu ), and the Jewish New Year are among well-known examples. India, Nepal, and other countries also celebrate New Year on dates according to their own calendars that are movable in the Gregorian calendar. During the Middle Ages in Western Europe , while the Julian calendar was still in use, authorities moved New Year's Day, depending upon locale, to one of several other days, including March 1, March 25, Easter, September 1, and December 25. Since then, many national civil calendars in
111-472: A technical writer for United Launch Alliance , has created at least 15,000 procedures for more than 300 missions since the Solar Maximum Mission , which launched Feb. 14, 1980. These documents are living documents, which reflect new issues and solutions as they develop. Each mission requires approximately 100 procedure books. Proceeding with the countdown depends on several factors, such as
148-407: A few seconds before T−0 and brought to full throttle around T−0. Solid rocket motors, which cannot be extinguished, are lit at T−0 and achieve full power a few seconds later. If a rocket has hold-down clamps which can withstand full engine thrust, the moment the clamps are released defines T−0. In Fritz Lang 's film Frau im Mond , after each number the phrase "seconds to go" was repeated. At
185-484: A launch, most countdown clocks begin to show Mission Elapsed Time , which is typically shown as "T plus." The adjacent picture shows "+00:00:07", approximately seven seconds after liftoff. The time T−0 is specifically the moment of launch commit , when it is no longer possible to prevent liftoff. This is necessarily slightly before the moment the rocket actually lifts off the launch pad. Liquid-fueled rocket engines (which can be turned off after ignition) are normally lit
222-515: A mission, all events after launch are scheduled on the Mission Elapsed Time. This avoids the constant rescheduling of events in case the launchtime slips. The MET-clock is set to zero at the moment of liftoff and counts forward in normal days, hours, minutes, and seconds. For example, 2:03:45:18 MET means it has been 2 days, 3 hours, 45 minutes, and 18 seconds since liftoff. MET was formerly called Ground Elapsed Time ( GET ) prior to
259-599: A rigid adherence to form was never mandated in the church. Nevertheless, the principal points of development were maintained between east and west. The Roman and Constantinopolitan liturgical calendars remained compatible even after the East-West Schism in 1054. Separations between the Catholic General Roman Calendar and Eastern Orthodox liturgical calendar grew only over several centuries' time. During those intervening centuries,
296-471: Is a carefully devised set of procedures ending with launch of a rocket. Depending on the type of vehicle used, countdowns can start from 72 to 96 hours before launch time. There are two countdowns proceeding simultaneously: Except for the last few minutes, which are highly automated and rigid, scheduled activities rarely take exactly the scheduled time, and the T-minus clock only corresponds approximately to
333-630: Is go. Mission Director : Kepler spacecraft is go. LC : SSC - FTS bat one and two heater controls heaters off. SSC : Off. LC : Prop 1, pressurized first stage LOX tanks to relief. Prop 1 : Pressurized. LC : Prop 2, top first stage LOX to 100 percent levels. Prop 2 : Up and down, 100 percent. Time : Ninety seconds. LC : SSC, hydraulic external power to on. SSC : External. Time : Eighty seconds. LC : RCO, report range go for launch. Range Control Officer (RCO) : Range go for launch. Mission Director : LC (Viera), you're go for launch. LC : Roger. In
370-662: The Byzantine calendar ). September 1 was used in Russia from 1492 (A.M. 7000) until the adoption of both the Anno Domini notation and 1 January as New Year's Day, with effect from 1700, via December 1699 decrees (1735, 1736) of Tsar Peter I . Because of the division of the globe into time zones , the new year moves progressively around the globe as the start of the day ushers in the New Year. The first time zone to usher in
407-705: The Coptic and Ethiopian Orthodox churches are unrelated to these systems but instead follow the Alexandrian calendar which fixed the wandering ancient Egyptian calendar to the Julian year . Their New Year celebrations on Neyrouz and Enkutatash were fixed; however, at a point in the Sothic cycle close to the Indiction ; between the years 1900 and 2100, they fall on September 11 during most years and September 12 in
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#1732794161336444-774: The Dormition of the Theotokos ("falling asleep" of the Virgin Mary , August 15). This last feast is known in the Roman Catholic church as the Assumption. The dating of "September 1" is according to the "new" (revised) Julian calendar or the "old" (standard) Julian calendar, depending on which is used by a particular Orthodox Church. Hence, it may fall on September 1 on the civil calendar, or on September 14 (between 1900 and 2099 inclusive). The liturgical calendars of
481-525: The Gregorian calendar , the most widely used calendar system today, New Year occurs on January 1 ( New Year's Day , preceded by New Year's Eve ). This was also the first day of the year in the original Julian calendar and the Roman calendar (after 153 BC). Other cultures observe their traditional or religious New Year's Day according to their own customs, typically (though not invariably) because they use
518-642: The Latin Church Catholic ecclesiastic year was moved to the first day of Advent , the Sunday nearest to St. Andrew's Day (November 30). By the time of the Reformation (early 16th century), the Roman Catholic general calendar provided the initial basis for the calendars for the liturgically oriented Protestants, including the Anglican and Lutheran Churches, who inherited this observation of
555-489: The Western World and beyond have changed to using one fixed date for New Year's Day, January 1—most doing so when they adopted the Gregorian calendar . Based on the used calendar new years are often categorized between lunar or lunisolar new years or solar new years . The new year of many South and Southeast Asian calendars falls between April 13–15, marking the beginning of spring. The early development of
592-698: The ecclesiastical calendar of the Roman Catholic Church came to be used as the beginning of the Julian year : Over the centuries, countries changed between styles until the Modern Style (January 1) prevailed. For example, A more unusual case is France, which observed the Northern autumn equinox day (usually September 22) as "New Year's Day" in the French Republican Calendar , which was in use from 1793 to 1805. This
629-582: The Christian liturgical year coincided with the Roman Empire (east and west), and later the Byzantine Empire , both of which employed a taxation system labeled the Indiction , the years for which began on September 1. This timing may account for the ancient church's establishment of September 1 as the beginning of the liturgical year, despite the official Roman New Year's Day of January 1 in
666-639: The Julian calendar, because the Indiction was the principal means for counting years in the empires, apart from the reigns of the Emperors. The September 1 date prevailed throughout all of Christendom for many centuries, until subsequent divisions eventually produced revisions in some places. After the sack of Rome in 410, communications and travel between east and west deteriorated. Liturgical developments in Rome and Constantinople did not always match, although
703-500: The Moon ) written by Thea von Harbou and directed by Fritz Lang in an attempt to increase the drama of the launch sequence of the story's lunar-bound rocket. People involved in countdowns always say that the last twenty minutes are the worst. By that time everything that needs doing has been done, and therefore everybody has twenty minutes in which to think of what may not have been done, or else what could possibly go wrong. A countdown
740-640: The New Year, just west of the International Date Line , is located in the Line Islands , a part of the nation of Kiribati , and has a time zone 14 hours ahead of UTC . All other time zones are 1 to 25 hours behind, most in the previous day (December 31); on American Samoa and Midway , it is still 11 pm on December 30. These are among the last inhabited places to observe New Year. However, uninhabited outlying US territories Howland Island and Baker Island are designated as lying within
777-735: The Space Shuttle, weather "outlooks" provided by the U. S. Air Force Range Weather Operations Facility at Cape Canaveral began at Launch minus 5 days in coordination with the NOAA National Weather Service Spaceflight Meteorology Group at the Johnson Space Center in Houston. These included weather trends and their possible effects on launch day. A formal prelaunch weather briefing was held on Launch minus 1 day, which
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#1732794161336814-536: The Space Shuttle. The International Space Station (ISS) does not use an MET clock since it is a "permanent" and international mission. The ISS observes Greenwich Mean Time (UTC/GMT). The shuttles also had UTC clocks so that the astronauts could easily figure out what the "official" time aboard ISS was. In 2019, a test flight of the Boeing CST-100 Starliner spacecraft suffered a mission anomaly through an incorrectly set Mission Elapsed Time on
851-473: The context of a rocket launch, the "L minus Time" is the physical time before launch, e.g. "L minus 3 minutes and 40 seconds". "T minus Time" is a system to mark points at which actions necessary for the launch are planned - this time stops and starts as various hold points are entered, and so doesn't show the actual time to launch. The last ten seconds are usually counted down aloud "Ten seconds to liftoff. Nine, eight, seven, six, five, four, three, two, one." After
888-418: The countdown is also used to celebrate independence day, with an event called Ambang Merdeka. The countdown was carried out at 11:59:50 pm and ended with chanting Merdeka 8 times and singing the national anthem . New Year The New Year is the time or day at which a new calendar year begins and the calendar's year count increments by one. Many cultures celebrate the event in some manner. In
925-458: The first frame of 2, which is accompanied by a 'pop.' This leader eventually displaced the older Academy and was the only leader used by the end of the optical (film) projection era. In many New Year's Eve celebrations, there is a countdown during the last seconds of the old year until the beginning of the new year. These countdowns usually end in fireworks . Some celebrations also have countdowns to midnight in preceding timezones. In Malaysia,
962-617: The liturgical new year. The present-day Eastern Orthodox liturgical calendar is the virtual culmination of the ancient eastern development cycle, though it includes later additions based on subsequent history and lives of saints. It still begins on September 1, proceeding annually into the Nativity of the Theotokos (September 8) and Exaltation of the Cross (September 14) to the celebration of Nativity of Christ (Christmas), through his death and resurrection (Pascha/Easter), to his Ascension and
999-478: The nearest or largest or most convenient political and economic locales with which each associate. By the time Howland Island sees the new year, it is 2 am on January 2 in the Line Islands of Kiribati. Mission Elapsed Time Mission Elapsed Time ( MET ) is used by NASA during their space missions, most notably during their Space Shuttle missions. Due to the fact that timing is very consequential in
1036-416: The proper launch window, weather that permits a safe launch, and the rocket and payload working properly. The launch weather guidelines involving the Space Shuttle and expendable rockets are similar in many areas, but a distinction is made for the individual characteristics of each. The criteria are broadly conservative and assure avoidance of possibly adverse conditions. They are reviewed for each launch. For
1073-478: The schedule if it is running long. Under some circumstances, a countdown may be recycled to an earlier time. When that happens, launch personnel begin following the countdown checklist from the earlier point. During countdown: The procedures for each launch are written carefully. For the Space Shuttle , a five-volume set, Shuttle Countdown (KSC S0007), often referred to as "S0007", was used. Rosie Carver,
1110-458: The start of films, a countdown sequence is printed on the head leader , and is used to synchronize film reel changeovers (switching between reels of film). In film (but not television) the 'Academy Leader' countdown first used in 1930 is in units of feet rather than time units; it starts at 11 and ends at 3 where it cuts to black for the last few feet. In 1959, SMPTE leader was created and measures seconds, not feet. It starts at 8 and cuts to black on
1147-798: The team for quick and positive identification of who is talking. For example, dialogue heard during the launch of a Delta II rocket carrying the Kepler Space Telescope on March 8, 2009, included: Time : T minus 3 minutes Launch Control (LC) : OSM, third stage S&A arm permit to close. Operations Safety Manager (OSM) : Closed. LC : SSC, third stage S&A armed. System Sequence Controller (SSC) : Armed. LC : Prop 1, vehicle fuel tank press open Prop 1 : Open. LC : Fuel umbilical purge to open. Prop 1 : Open. LC : SSC, vent 1 heater control exit. SSC : Exit. LC : SSC, vent 2 heater control exit. SSC : Exit. LC : NSC reports spacecraft
Countdown - Misplaced Pages Continue
1184-506: The time until launch. A hold is the suspension of the normal countdown process, during which the T-minus clock is stopped and no planned activities take place. This can be done to investigate a technical process that has gone wrong, or to intentionally delay the launch, e.g. because of bad weather at the launch pad. Most countdown schedules also include some pre-planned built-in holds . These provide an opportunity to perform non-launch activities, handle unexpected issues, or to catch up on
1221-552: The time zone 12 hours behind UTC, the last places on Earth to see the arrival of January 1. These small coral islands are found about midway between Hawaii and Australia, about 1,000 miles west of the Line Islands. This is because the International Date Line is a composite of local time zone arrangements, which winds through the Pacific Ocean, allowing each locale to remain most closely connected in time with
1258-519: The years preceding a leap year . During the Roman Republic and the Roman Empire , years began on the date on which each consul first entered the office. This was probably May 1 before 222 BC, March 15 from 222 BC to 154 BC, and January 1 from 153 BC. In 45 BC, when Julius Caesar 's new Julian calendar took effect, the Senate fixed January 1 as the first day of the year. At that time, this
1295-510: Was primidi Vendémiaire , the first day of the first month. It took quite a long time before January 1 again became the universal or standard start of the civil year. The years of adoption of January 1 as the new year are as follows: March 1 was the first day of the numbered year in the Republic of Venice until its destruction in 1797, and in Russia from 988 until 1492 ( Anno Mundi 7000 in
1332-423: Was a specific weather briefing for all areas of Space Shuttle launch operations. The launch window is a precise time during which aerospace personnel launch a rocket so the payload can reach the proper orbital destination. During communications for a countdown, the launch team uses acronyms to keep channels open as much as possible. All Firing Room console positions are assigned unique 'call signs' that are used by
1369-585: Was the date on which those who were to hold civil office assumed their official position, and it was also the traditional annual date for the convening of the Roman Senate. This civil new year remained in effect throughout the Roman Empire, east and west, during its lifetime and well after, wherever the Julian calendar continued in use. In the Middle Ages in Europe a number of significant feast days in
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