October 2002
George Diller
Kennedy Space Center
321/867-2468
RELEASE: 92-02
SPACE SHUTTLE WEATHER LAUNCH COMMIT CRITERIA AND KSC END OF MISSION WEATHER LANDING CRITERIA
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 the Space Shuttle, weather forecasts are provided by the U. S. Air
Force Range Weather Operations Facility at Cape Canaveral beginning
at Launch minus 3 days in coordination with the NOAA National Weather
Service Space Flight Meteorology Group (SMG) at the Johnson Space
Center in Houston. These include weather trends and their possible
effects on launch day. A formal prelaunch weather briefing is held on
Launch minus 2 days which is a specific weather briefing for all
areas of Space Shuttle launch operations.
Launch weather forecasts, ground operations forecasts, and launch
weather briefings for the Mission Management Team and the Space
Shuttle Launch Director are prepared by the Range Weather Operations
Facility. Forecasts which apply after launch are prepared by SMG.
These include all emergency landing forecasts and the end of mission
forecasts briefed by SMG to the astronauts, the Flight Director and
Mission Management Team.
During the countdown, formal weather briefings occur approximately as
follows:
L-24 hr 0 min: Briefing for Flight Director and astronauts
L-21 hr 0 min: Briefing for removal of Rotating Service Structure
L-9 hr 00 min: Briefing for external tank fuel loading
L-4 hr 30 min: Briefing for Space Shuttle Launch Director
L-3 hr 55 min: Briefing for astronauts
L-2 hr 10 min: Briefing for Flight Director
L-0 hr 35 min: Briefing for launch and RTLS
L-0 hr 13 min: Poll all weather constraints
The basic weather launch commit criteria on the pad at liftoff must
be:
Temperature: Prior to external tank propellant loading, tanking will
not begin if the 24 hour average temperature has been below 41
degrees.
After tanking begins, the countdown shall not be continued nor the
Shuttle launched if:
a.) the temperature exceeds 99 degrees for more than 30 consecutive
minutes.
b.) the temperature is lower than the prescribed minimum value for
longer than 30 minutes unless sun angle, wind, temperature and
relative humidity conditions permit recovery. The minimum temperature
limit in degrees F. is specified by the table below and is a function
of the five minute average of temperature, wind and humidity. The
table becomes applicable when the observed temperature reaches 48
degrees.
Wind Speed
Relative Humidity
(kts)0-64%65-74%75-79%80-89%90-100%
0 - 14847464544
24746454443
34141414039
43939393938
5 - 73838383838
8 - 143737373737
>143636363636
The above table can be used to determine when conditions are again
acceptable for launch if parameters have been out of limits for
thirty minutes or less. If longer than thirty minutes, a mathematical
recovery formula of the environmental conditions is used to determine
if a return to acceptable parameters has been achieved. Launch
conditions have been reached if the formula reaches a positive value.
Wind: Tanking will not begin if the wind is observed or forecast to
exceed 42 knots for the next three-hour period.
For launch the wind constraints at the launch pad will vary slightly
for each mission. The peak wind speed allowable is 30 knots. However,
when the wind direction is between 100 degrees and 260 degrees, the
peak speed varies for each mission and may be as low as 24 knots.
The upper atmosphere wind profile must conform to either one of two
wind loading programs developed by the Johnson Space Center. This
profile is determined by a series of Jimsphere wind balloon releases
from Cape Canaveral Air Station. A final recommendation is made by
the JSC Launch Systems Evaluation Advisory Team (LSEAT) to the KSC
launch director at Launch minus 30 minutes. The Space Shuttle will
not be launched within 30 minutes of the time a determination has
been made that the upper wind profile will adversely affect the
performance of the launch vehicle.
A downrange weather advisory shall be issued by the Shuttle Weather
Officer to the Mission Management Team for their consideration if the
wind in the solid rocket booster recovery area is forecast to exceed
26 knots during retrieval operations. Seas in excess of Sea State 5
(8-13 feet) may also be a factor considered by the Mission Management
Team.
Precipitation: None at the launch pad or within the flight path.
Lightning (and electric fields with triggering potential):
- Tanking will not begin if there is forecast to be greater than a 20%
chance of lightning within five nautical miles of the launch pad
during the first hour of tanking. The launch director with the
concurrence of the safety director may make an exception after
consultation with the Shuttle Weather Officer.
- Do not launch if lightning has been detected within 10 nautical
miles of the pad or the planned flight path within 30 minutes prior
to launch. Launch may occur if the source of lightning has moved more
than 10 nautical miles away from the pad or the flight path and a
field mill, used to measure electric fields, is located within 5
nautical miles of the lightning flash.
- The one-minute average of the electric field mill network may not
exceed -1 or +1 kilovolt per meter within five nautical miles of the
launch pad or the lightning flash at any time within 15 minutes prior
to launch. This field mill criteria becomes -1.5 or + 1.5 kilovolts
per meter if there are no clouds within 10 nautical miles of the
flight path except those which are transparent. Also excepted are
clouds with tops below the 41 degrees F. temperature level that have
not have been previously associated with a thunderstorm, or
associated with convective clouds having tops above the 14 degrees F.
temperature level during the last three hours.
- Do not launch when lightning is observed and the cloud which
produced the lightning is within 10 nautical miles of the flight
path. Launch may not occur until 30 minutes has elapsed since the
lightning flash, or the cloud has moved more than 10 nautical miles
away.
Clouds: (types known to contain hazardous electric fields)
- Do not launch if any part of the planned flight path is through a
layer of clouds any part of which is within 5 nautical miles is 4,500
feet thick or greater and the temperature of any part of the layer is
between 32 degrees F. and -4 degrees F. Launch may occur if the cloud
layer is a cirrus-like cloud that has never been associated with
convective clouds, is located entirely at temperatures of 5 degrees
F. or colder, and shows no evidence of containing water droplets.
- Do not launch through cumulus type clouds with tops higher than the
41 degree F. temperature level. Launch may occur through clouds as
cold as 23 degrees F. if the cloud is not producing precipitation,
and all field mills within 5 nautical miles of the flight path and at
least one field mill within 2 nautical miles of the cloud center read
between -100 volts per meter and +500 volts per meter.
- Do not launch 1.) through or within 5 nautical miles of the nearest
edge of cumulus type clouds with tops higher than the 14 degree F
level; 2) through or within 10 nautical miles of the nearest edge of
cumulus clouds with tops higher than the -4 degrees F. level.
- Do not launch if the flight path is through any non-transparent
clouds that extend to altitudes at or above the 32 degrees F. level
which are associated with disturbed weather producing moderate or
greater precipitation, or melting precipitation, within five nautical
miles of the flight path.
- Do not launch through an attached anvil cloud. If lightning occurs
in the anvil or the associated main cloud, do not launch within 10
nautical miles for the first 30 minutes after lightning is observed,
or within 5 nautical miles from 30 minutes to 3 hours after lightning
is observed.
- Do not launch if the flight path will carry the vehicle:
a.) through non-transparent parts of a detached anvil for the first
three hours after the anvil detaches from the parent cloud, or the
first four hours after the last lightning occurs in the detached
anvil.
b.) within 10 nautical miles of non-transparent parts of a detached
anvil for the first thirty minutes after the time of the last
lightning in the parent or anvil cloud before detachment, or the
detached anvil after its detachment.
c.) within 5 nautical miles of non-transparent parts of a detached
anvil for the first three hours after the time of the last lightning
in the parent or anvil cloud before detachment, or the detached anvil
after detachment, unless there is a field mill within 5 nautical
miles of the detached anvil reading less than 1,000 volts per meter
for the last 15 minutes and a maximum radar returns from any part of
the detached anvil within 5 nautical miles of the flight path have
been less than 10 dBZ (light rain) for 15 minutes.
- Do not launch if the flight path will carry the vehicle through a
thunderstorm or cumulonimbus debris cloud which is not transparent
and less than three hours old. Launch may not occur within five
nautical miles of these debris clouds unless: 1) for 15 minutes
preceding launch there is at least one working field mill within five
nautical miles of the debris cloud; 2) all electric field mill
readings are between -1 kilovolt and + 1 kilovolt per meter within
five nautical miles of the flight path; 3) no precipitation has been
detected in the debris cloud (less than 10 dbz by radar) within 5
nautical miles of the flight path.
- Do not launch if the flight path will carry the vehicle through any
cumulus cloud that has developed from a smoke plume while the cloud
is attached to the plume, or for the first 60 minutes after the
cumulus cloud detaches from the smoke plume.
Supporting Table: KSC Seasonal Altitudes of Temperature Levels in
thousands of feet
| January | July
TempLowAvgHighTempLowAvgHigh
-4 F21 Kft24 Kft26 Kft-4 F23 Kft27 Kft29 Kft
1413182114182123
239151823161820
32sfc121632131518
41sfc91441101215
Range Safety Cloud Ceiling and Visibility constraints:
- Direct visual observation of the Shuttle is required through 8,000
feet. This requirement may be satisfied using optical tracking sites
or a forward observer
- For cloud ceilings of any thickness between 6, 000 feet and 8,000
feet the following conditions must be met for launch to occur:
a.) the vehicle integrity can be observed without interruption through
6,000 feet.
b.) all required Range Safety instrumentation is functioning properly
c.) the U.S. Air Force 45th Space Wing Commander approves the decision
to proceed
- For cloud ceilings between 4,000 feet and 6,000 feet the following
conditions must be met for launch to proceed:
a.) the thickness of the clouds must be less than 500 feet
b.) the vehicle integrity can be monitored by the Eastern Range
airborne and/or the ground forward observers through 8,000 feet
c.) all required Range Safety instrumentation is functioning properly
d.) the U.S. Air Force 45th Space Wing Commander approves the decision
to proceed
A "Good Sense Rule" is in effect for launch which states:
"Even when constraints are not violated, if any other hazardous
conditions exist, the launch weather officer will report the threat
to the launch director. The launch director may hold at any time
based on the instability of the weather."
CONTINGENCY FLIGHT RULES
Weather criteria for an emergency landing must be considered along
with launch criteria since the possibility exists for a Return To
Launch Site abort (RTLS), landings at the Trans-Oceanic Abort Landing
Sites (TAL), the Abort Once Around (AOA) sites and the first day
Primary Landing Site (PLS). These forecasts are prepared by the NOAA
National Weather Service Spaceflight Meteorology Group in Houston and
briefed by them to the astronauts, Flight Director and Mission
Management Team. All criteria refer to observed and forecast weather
conditions except for the first day PLS which is forecast weather
only.
- For RTLS with redundant Microwave Landing System (MLS) capability
and a weather reconnaissance aircraft, cloud coverage 4/8 or less
below 5,000 feet and a visibility of 4 statute miles or greater are
required. For AOA and PLS sites, cloud coverage 4/8 or less below
8,000 feet and a visibility of 5 statute miles or greater is
required. For TAL sites, cloud coverage 4/8 or less below 5,000 feet
and a visibility of 5 statute miles or greater are required.
- For landing on a hard surface runway without redundant Microwave
Landing System (MLS) capability all sites require a ceiling not less
than 10,000 feet and a visibility of at least 7 statute miles.
Landing at night on a lake bed runway may occur if the ceiling is not
lower than 15,000 feet and the visibility is 7 miles or greater with
at least non-redundant MLS capability.
- For the RTLS site and TAL sites, no thunderstorms, lightning, or
precipitation within 20 nautical miles of the runway, or within 10
nautical miles of the final approach path extending outward to 30
nautical miles from the end of the runway.
- An RTLS rule exception may be made for light precipitation within 20
nautical miles of the runway if the specific criteria listed below
are met:
a.) The tops of the clouds containing precipitation do not extend into
temperature regions colder than 41 (F.); they have not been colder
than 14 (F.) within 2.5 hours prior to launch; the radar reflectivity
is less than 30 dbz at all levels within and below the clouds.
b.) Precipitation covers less than 10% of the area within 20 nautical
miles of the runway, or multiple heading alignment circles are clear
of showers.
c.) The movement of the showers is observed to be consistent and no
additional convective development is forecast.
d.) Touchdown/rollout criteria and associated navigational aids meet
the specified prelaunch go/no go requirements.
If showers exceed either parameter of part a.) above, an RTLS landing
may still occur if a 2 nautical mile vertical clearance can be
maintained from the top of any shower within 10 nautical miles of the
approach paths.
- For RTLS and TAL sites, no detached opaque thunderstorm anvils less
than three hours old within 15 nautical miles of the runway, or
within 5 nautical miles of the final approach path extending outward
to 30 nautical miles from the end of the runway.
- For AOA and PLS sites, no thunderstorms, lightning or precipitation
within 30 nautical miles of the runway, or within 20 nautical miles
of the final approach path extending to 30 nautical miles from the
end of the runway.
- For RTLS and the TAL sites, no detached opaque thunderstorm anvil
cloud less than 3 hours old within 15 nautical miles of the runway or
within 5 nautical miles of the final approach path extending outward
to 30 nautical miles from the end of the runway.
- For AOA and PLS sites, no detached opaque thunderstorm anvil cloud
less than 3 hours old within 20 nautical miles of the runway or
within 10 nautical miles of the final approach path extending to 30
nautical miles from the end of the runway.
- The RTLS, TAL, AOA and PLS crosswind component may not exceed 15
knots. For RTLS, if the astronaut flying weather reconnaissance in
the Shuttle Training Aircraft flys the approach and considers the
landing conditions to be acceptable, this limit may be increased to
17 knots. For the PLS landing sites there is a night-time crosswind
limit of 12 knots.
- Headwind: not to exceed 25 knots.
- Tailwind: not to exceed 10 knots average, 15 knots peak.
- Turbulence: conditions must be less than or equal to moderate
intensity.
KSC END OF MISSION LANDING WEATHER FLIGHT RULES
The end of mission landing weather forecast is prepared by the NOAA
National Weather Service Space Flight Meteorology Group in Houston
for the astronauts, Flight Director and Mission Management Team. All
criteria refer to observed and forecast weather conditions. Decision
time for the deorbit burn is 70 - 90 minutes before landing. The
weather criteria are:
- Cloud coverage of 4/8 or less below 8,000 feet and a visibility of 5
miles or greater required.
- The peak cross wind cannot exceed 15 knots, 12 knots at night. If
the mission duration is greater than 20 days the limit is 12 knots,
day and night.
- Headwind cannot exceed 25 knots.
- Tailwind cannot exceed 10 knots average, 15 knots peak.
- No thunderstorm, lightning, or precipitation activity is within 30
nautical miles of the Shuttle Landing Facility.
- Detached opaque thunderstorm anvils less than three hours old must
not be within 20 nautical miles of the Shuttle Landing Facility, or
within 10 nautical miles of the flight path when the orbiter is
within 30 nautical miles of the runway.
- Turbulence must be less than or equal to moderate intensity.
- Consideration may be given for landing with a "no go" observation
and a "go" forecast if at decision time analysis clearly indicates a
continuing trend of improving weather conditions, and the forecast
states that all weather criteria will be met at landing time.
WEATHER INSTRUMENTATION
The weather equipment used by the forecasters to develop the launch
and landing forecasts is:
-Radar: Launch forecasters located at Cape Canaveral Air Force Station
and landing forecasters located in Houston can access displays from
two different radars. One is located at Patrick Air Force Base near
Cocoa Beach. The other is located in Melbourne at the NOAA National
Weather Service and is a NEXRAD Doppler radar. Each radar provides
rain intensity and cloud top information out to a distance as far as
200 nautical miles. The NEXRAD radar can also provide estimates of
total rainfall and radial wind velocities.
-Launch Pad Lightning Warning System (Field Mill Network): Thirty-one
advanced field mill sites around KSC and Cape Canaveral Air Force
Station provide data on lightning activity and surface electric
fields induced by charge aloft. This data helps forecasters determine
when electric charge aloft may be sufficient to create triggered
lightning during launch, and to determine when to issue and cancel
lightning advisories and warnings.
-Cloud to Ground Lightning Surveillance System (CGLSS): Detects and
plots cloud to ground lightning strikes within 125 nautical miles of
the Kennedy Space Center. Location accuracy is optimum within 30
nautical miles. Locations of strikes are color coded according to
time of occurrence.
-Lightning Detection And Ranging (LDAR): Developed by NASA at the
Kennedy Space Center, LDAR plots intracloud, cloud to cloud and cloud
to ground lightning in three dimensions within 75 statute miles of
the Kennedy Space Center. Location accuracy is very high within 25
statute miles. LDAR data is important in determining the beginning
and end of lightning conditions.
-National Lightning Detection Network: Plots cloud to ground lightning
nationwide. Used to help ensure safe transit of the Space Shuttle
orbiter atop the Shuttle Carrier Aircraft between Edwards Air Force
Base in California and the Kennedy Space Center in Florida. It is
also used to assess lightning beyond the 125 mile range of the
Lightning Detection System.
-Rawinsonde: A balloon with a tethered instrument package which radios
its altitude to the ground together with temperature, dewpoint and
humidity, wind speed and direction, and pressure data. Rawinsondes
reach altitudes exceeding 100,000 feet.
-Jimsphere balloon: A reflective balloon made of mylar tracked by
radar which provides highly accurate information on wind speed and
wind direction up to 60,000 feet.
-Doppler Radar Wind Profiler: Measures upper level wind speed and
direction over Kennedy Space Center from approximately 10,000 feet to
60,000 feet. The data, received every 5 minutes, is used to ensure
the upper winds used to calculate wind loads on the shuttle vehicle
have not significantly changed between balloon soundings. If data
from the Doppler Radar Wind Profiler indicates a possible significant
change, another Jimsphere balloon is released.
-Rocketsonde: If necessary, a 12-foot-tall instrumented rocket is
launched on L-1 day which senses and transmits data on temperature,
wind speed and direction, wind shear, pressure, and air density at
altitudes between 65,000 feet and 370,000 feet. A four-inch in
diameter solid rocket motor separates at an altitude of about 5,000
feet, after which an "instrumented dart" coasts to apogee.
-Satellite Images and Data: Provided directly to the satellite
terminal at USAF Range Weather Operations and NOAA National Weather
Service Space Flight Meteorology Group in Houston by the
geostationary GOES weather satellites. In addition high resolution
images are received from spacecraft in low earth orbit including both
the NOAA and the Defense Meteorological Support Program (DMSP) polar
orbiting satellites.
-Meteorological Interactive Data Display System (MIDDS): Integrates
diverse weather data on a single display terminal-- satellite images,
radar, computer generated graphics of surface and upper air map
features, numerical weather models, current weather observations,
data from meteorological towers, lightning strikes and field mill
information.
-Towers: 33 meteorological towers are located on Kennedy Space Center
and Cape Canaveral Air Force Station, including two at each launch
pad and three at the Shuttle Landing Facility. In addition to wind,
most towers are also instrumented with temperature, and moisture
sensors. The 60-foot towers at the launch pads and the 33-foot towers
at the Shuttle Landing Facility are closely monitored for launch and
landing criteria. In addition, on the mainland, there is a network of
19 wind towers which extend outward an additional twenty miles. Tower
data is an important short-term forecasting tool and also helps
determine the direction and distance of toxic corridors in the event
of a mishap.
-Buoys: Meteorological buoys are anchored 20 and 110 nautical miles
east-northeast of Cape Canaveral. These buoys relay hourly
measurements via satellite of temperature, wind speed and direction,
barometric pressure, precipitation, sea water temperature, and wave
height and period. Buoy data is used for launch, landing, booster
retrieval, and daily ground processing forecasts for the Kennedy
Space Center and Cape Canaveral Air Station.
-Solid Rocket Booster Retrieval Ships: These vessels radio observed
weather conditions and sea state from the booster impact area located
up to 150 nautical miles downrange.
-Weather Reconnaissance Aircraft: A T-38 jet and the Shuttle Training
Aircraft are flown by a weather support astronaut.
-end-
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