July 1, 1997
KSC Contact: George H. Diller
KSC Release No. 98-97
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 "outlooks" provided by the U. S. Air
Force Range Weather Operations Facility at Cape Canaveral begin at
Launch minus 5 days in coordination with the NOAA National Weather
Service Spaceflight 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
1 day 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
During the countdown, formal weather briefings occur approximately as
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
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. In no case
may the Space Shuttle be launched if the temperature is 35 degrees or
|Wind Speed||Relative Humidity
|0 - 1||48||47||46||45||44
|5 - 7||38||38||38||38||38
|8 - 14||37||37||37||37||37
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 34 knots. However,
when the wind direction is between 100 degrees and 260 degrees, the peak
speed varies and may be as low as 20 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
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
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.
- Launch will not occur if lightning has been detected within 10
nautical miles of the pad or the planned flight path within 30 minutes
prior to launch, unless the source of lightning has moved more than 10
nautical miles away from the pad or the flight path.
- The one-minute average of the electric field mill network, used to
measure electric fields, shall not exceed -1 or +1 kilovolt per meter
within five nautical miles of the launch pad at any time within 15
minutes prior to launch.
The above rule need not apply if the following two conditions are
observed to exist:
1. 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.
2. A known source of electric fields such as ground fog, smoke or
"sunrise effect" is occurring near the field mill which are conditions
previously determined and documented to be benign and is clearly causing
the elevated readings.
Clouds: (types known to contain hazardous electric fields)
- The Space Shuttle may not be launched if the planned flight path is
through a layer of clouds with a thickness of 4,500 feet or greater
where the temperature of any part of the layer is between 32 degrees F.
and -4 degrees F.
- The Space Shuttle may not be launched if the planned flight path is
through a cumulus type cloud with its top between the 41 degrees F.
temperature level and 23 degrees F. temperature. Launch may occur if:
1) the cloud is not producing precipitation; 2) the distance from the
furthest edge of the cloud top to at least one operating field mill is
less than the altitude at the 23 degree F temperature level or 3
nautical miles, whichever is less; 3) field mill readings within five
nautical miles of the flight path must be between -100 volts per meter
and +1000 volts per meter.
- The Space Shuttle may not be launched through 1) cumulus type clouds
with tops higher than the 23 degree F. temperature level; 2) through or
within 5 nautical miles of the nearest edge of cumulus type clouds with
tops higher than the 14 degree F level; 3) through or within 10 nautical
miles of the nearest edge of any cumulonimbus or thunderstorm cloud
including nontransparent parts of its anvil; 4) through or within 10
nautical miles of the nearest edge of a nontransparent detached anvil
cloud for the first hour after detachment from the parent thunderstorm
or cumulonimbus cloud.
- The Space Shuttle may not be launched if the flight path is through
any clouds that extend to altitudes at or above the 32 degrees F. level
which are associated with disturbed weather producing moderate or
greater precipitation within five nautical miles of the flight path.
- The Space Shuttle may not be launched 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
Supporting Table: KSC Seasonal Altitudes of Temperature Levels in
thousands of feet
|-4 F||21 Kft||24 Kft||26 Kft||-4 F||23 Kft||27 Kft||29 Kft
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
- 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
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
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
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
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
KSC END OF MISSION LANDING WEATHER FLIGHT RULES
- 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
- 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 crosswind component may not exceed 15 knots. If the
astronaut flying weather reconnaissance in the Shuttle Training Aircraft
executes the approach and considers the landing conditions to be
acceptable, this limit may be increased to 17 knots. For the TAL, AOA
and PLS 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
The end of mission landing weather forecast is prepared by the NOAA
National Weather Service Spaceflight Meteorology Group in Houston for
the astronauts, Flight Director and Mission Management Team. All
criteria refer to observed and forecast weather conditions. At decision
time for the deorbit burn 90 minutes before landing the weather
conditions must be:
- Cloud coverage of 4/8 or less below 8,000 feet and a visibility of 5
miles or greater is required.
- The peak cross wind cannot exceed 15 knots, 12 knots at night. If
the mission duration is greater than 12 days the limit is 12 knots, day
- 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.
- Vertical clearance from the tops of rain showers or thunderstorms
must be greater than 2 nautical miles 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.
- The Flight Director must consider a possible "no go" to landing if
at the deorbit burn decision time there are observed to be scattered
cloud layers below 8,000 feet with greater than 2/8 sky coverage but
not exceeding 4/8 sky coverage. Cloud conditions greater than 4/8 sky
coverage below 8,000 feet constitute a cloud ceiling and is therefore
The weather equipment used by the forecasters to develop the
launch and landing forecasts is:
- Radar: Launch forecasters located at Cape Canaveral Air Station and
landing forecasters located in Houston can access displays from two
different radar. One is located at Patrick Air Force Base south of
Cocoa Beach. The other is located in Melbourne at the 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.
- Field Mill Network: Thirty-one advanced field mill sites around KSC
and Cape Canaveral Air 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.
- Lightning Detection System: 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 100 nautical miles of the
Kennedy Space Center. Location accuracy is very high within 25 nautical
miles. LDAR data is important in determining the beginning and end of
- 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
- 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: 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
Spaceflight 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
- Towers: 33 meteorological towers are located on Kennedy Space Center
and Cape Canaveral Air 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, 110 and 160 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.
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