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.
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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