George
Diller
January 2003
Kennedy Space Center, Fla.
(321) 867-2468
KSC
Release No. 13 - 03
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.
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 - 1 | 48 | 47 | 46 | 45 | 44 |
| 2 | 47 | 46 | 45 | 44 | 43 |
| 3 | 41 | 41 | 41 | 40 | 39 |
| 4 | 39 | 39 | 39 | 39 | 38 |
| 5 - 7 | 38 | 38 | 38 | 38 | 38 |
| 8 - 14 | 37 | 37 | 37 | 37 | 37 |
| >14 | 36 | 36 | 36 | 36 | 36 |
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 on
radar (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 | ||||||
|---|---|---|---|---|---|---|---|
| Temp | Low | Avg | High | Temp | Low | Avg | High |
| -4 F | 21 Kft | 24 Kft | 26 Kft | -4 F | 23 Kft | 27 Kft | 29 Kft |
| 14 | 13 | 18 | 21 | 14 | 18 | 21 | 23 |
| 23 | 9 | 15 | 18 | 23 | 16 | 18 | 20 |
| 32 | sfc | 12 | 16 | 32 | 13 | 15 | 18 |
| 41 | sfc | 9 | 14 | 41 | 10 | 12 | 15 |
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."
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 Space Flight 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.) The runway meets the landing/rollout criteria and the navigational aid requirements specified in the 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.
- A TAL rule exception may be made for rain showers if continuous radar and aircraft surveillance indicates the following conditions are met:
a.) Showers cover less than 10 per cent of the area within 20 nautical miles of the runway.
b.) Observed horizontal movement is consistent and no additional convective development is forecast.
c.) Tops of clouds containing precipitation are not colder than 41 (F.) and have not been colder than 14 (F.) within 2.5 hours prior to launch.
d.) Precipitation is light (less than 30 dbz on radar) at all levels within and below the cloud.
e.) If any shower within 20 nautical miles of the runway exceeds the previous two requirements, then a 2 nautical mile vertical clearance from the top of the shower and a 10 nautical mile lateral clearance must be maintained along the approach corridors.
f.) The runway meets the landing/rollout criteria and the navigational aid requirements specified in the prelaunch go/no-go requirements.
g.) There is a high level of confidence at least one approach (overhead or straight-in) will be acceptable at the time of touchdown and radar and aircraft indicate that a stable and predictable environment exists.
- 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 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.
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 de-orbit 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.
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 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 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.
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