June 22, 1995

KSC Release No. 61-95

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.

	Weather "outlooks"  which are provided by the Range Weather
Operations Facility at Cape Canaveral begin at Launch minus 5 days. 
These include weather trends, and their possible effects on launch
day.

	For the Space Shuttle, 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.

	During the countdown, formal weather briefings occur
approximately as follows:

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-0 hr 35 min: Briefing for launch and RTLS
L-0 hr 13 min: Poll all weather constraints

	The basic weather parameters 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 will not continue if
the temperature exceeds 99 degrees for more than 30 consecutive
minutes.

	After tanking begins, the countdown shall not be continued
nor the Shuttle launched if the temperature is lower than the
prescribed minimum value for longer than 30 minutes unless sun, wind
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 colder.

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, when the wind direction at the launch pad is
between 300 degrees and 060 degrees, the highest wind allowable is 34
knots.  When the wind direction is between 150 degrees and 200
degrees, the highest wind allowable is 20 knots.  The peak allowable
wind speeds are on a descending scale between the directions of 060
degrees and 150 degrees, and an ascending scale between 200 degrees
and 300 degrees.

	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.


Precipitation: None at the launch pad or within the flight path.

Lightning (and electric fields with triggering potential):

 - Tanking will not begin if lightning is observed within five
nautical miles of the launch pad or is forecast to occur during the
first hour of tanking.

 - 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 or
smoke that is occuring near the field mill which has been previously
determined and documented to be benign is clearly causing the
elevated readings.


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

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 or observed.


	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 LANDING CRITERIA


	Weather conditions for a landing also affect the launch
criteria since the possibility exists for a Return To Launch Site
abort (RTLS) at the Kennedy Space Center or for emergency landings at
other off-site locations.

	The landing criteria for the Trans-Oceanic Abort Sites (TAL),
and the Abort Once Around (AOA) sites of Edwards Air Force Base, and
White Sands Space Harbor are:

 - Cloud coverage 5 tenths or less below 8,000 feet with a clear line
of sight to the end of the runway.

 - No detached opaque thunderstorm anvil cloud within 10 nautical
miles of the runway or within 5 nautical miles of the final approach
path extending to 30 nautical miles distance.

 - For RTLS and the 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.

 - For RTLS, a ceiling of 5,000 feet and a visibility of 4 nautical
miles or greater is required.

 - Visibility for the TAL sites and AOA, 5 statute miles or greater
where microwave landing system (MLS) instrument landing capability is
available; otherwise 7 statute miles.

 - Crosswind component for Return to Launch Site (RTLS) not to exceed
15 knots.  For Abort Once Around (AOA) and Trans-Oceanic (TAL)
contingency landing sites the night-time crosswind limit is 12 knots.

 - Headwind not to exceed 25 knots

 - Tailwind not to exceed 10 knots average, 15 knots peak

 - Sun angle on final approach not within 10 degrees in azimuth and 0
to 20 degrees in elevation


KSC END OF MISSION LANDING WEATHER CRITERIA


At decision time for the deorbit burn 90 minutes before landing:

 - The visibility must be observed and forecast to be 5 nautical
miles or greater.

 - The peak wind speed, regardless of direction, may not be observed
or forecast to exceed 20 knots.

 - The peak cross wind shall not be observed or forecast to exceed 15
knots, 12 knots at night.  If the mission duration is greater than 12
days the limit is 12 knots, day or night.

 - An observed or forecast cloud ceiling must be 10,000 feet or higher.

 - Observed scattered cloud layers below 10,000 feet must not exceed
2/10 sky coverage.

 - At a range of 30 nautical miles, vertical clearance from the tops
of rain showers or thunderstorms must be greater than 2 nautical
miles.

 - Landing in or near precipitation is not acceptable.

 - The deorbit burn shall not occur if thunderstorm, lightning, or
precipitation activity is observed within 30 nautical miles of the
Shuttle Landing Facility.

 - Detached opaque thunderstorm anvils less than three hours old must
not be observed or forecast to 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.


WEATHER INSTRUMENTATION


	The equipment used by the forecaster to develop the downrange
and launch clearance forecast are:

 -Radar:  The color weather radar display is located at the Cape
Canaveral Forecast Facility.  The antenna is located on Patrick Air
Force Base in Cocoa Beach.  Echo returns and information about rain
intensity and cloud tops may be observed up to a distance of 200
nautical miles.  Also available to the Shuttle Weather Officer is a
display of the National Weather Service doppler weather radar located
in Melbourne.

 -Field Mill Network:  Thirty-one advanced field mill sites around
KSC and Cape Canaveral Air  Station provide a contour map of electric
fields and lightning activity.  This tool assists the forecaster in
determining that the lightning avoidance criteria are met.

 -Lightning Detection System:  Plots cloud to ground lightning
strikes within 125 miles of the Range Weather Facility.

 -Lightning Detection And Ranging (LDAR):  A new system developed by
NASA undergoing evaluation, LDAR is a three dimensional system that
plots intracloud, cloud to cloud and cloud to ground lightning with
high demonstrated accuracy within 25 nautical miles but recording
lightning events up to 100 nautical miles distant from Cape
Canaveral.

 -Rawinsonde:  A balloon with a tethered instrument package which
radios to the ground its altitude with weather data on temperature,
dewpoint and humidity, wind speed and direction,  and pressure.  A
rawinsonde may reach an altitude as high as 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.

 -Rocketsonde:  On L-1 day, a 12-foot-tall instrumented rocket is
launched.  It returns data on temperature, wind speed and direction,
wind shear,  pressure, and air density at the altitude region 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 in the Range Weather Facility by the GOES weather
satellites, and also high resolution pictures from polar low earth
orbiting spacecraft including both the NOAA polar orbiters and the
Defense Meteorological Support Program (DMSP) satellites.

 -Meteorological Interactive Data Display System (MIDDS):  Integrates
for the forecaster on a single visual display the satellite images,
computer generated graphics of surface and upper air map features,
and current weather observations.  The system will also display or
plot and contour various meteorological parameters, and can display
any selected current National Weather Service radar picture.

 -Wind towers:  A total of 33 wind 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 sensors. 
The 60-foot wind towers at the launch pads and the 10-meter wind
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 and are used as a tool in short-term forecasting.

 -Instrumented Weather Buoys:  Anchored East-Northeast of Cape
Canaveral, two meteorological buoys are stationed at distances of 25
nautical miles and 110 nautical miles.  Offshore weather conditions
may be influencing onshore weather. These ocean weather buoys relay
hourly reports by satellite and are received at the Range Weather
Facility.  Measurements include air temperature, wind speed and
direction, barometric pressure, precipitation, sea water temperature,
and the wave height with period.

 -Solid Rocket Booster Retrieval Ships:  These vessels radio observed
weather conditions and sea state from the booster impact area located
approximately 160 miles downrange.

 -Weather Reconnaissance Aircraft:  A T-38 jet and the Shuttle
Training Aircraft are flown by a weather support astronaut.



NOTE: The launch weather forecast is prepared by the U.S. Air Force
Range Weather Operations Facility at Cape Canaveral.  The landing and
RTLS forecast is prepared by the NOAA Space Flight Meteorology Group
at the Johnson Space Center in Houston.