Weather balloons and rocket science

VANDENBERG AIR FORCE BASE, Calif. -- For every launch from Vandenberg, monitoring the weather is paramount to a safe, successful mission. Sometimes, despite seemingly optimal conditions, the upper atmosphere or weather further downrange may be less than cooperative.

The weather flight follows a set of rules as well as specific guidance from each launch customer, who may have different weather thresholds, to decide whether it is safe to continue with the launch process or if a delay should be instituted.

"For every launch, the Launch Weather Team interrogates the atmosphere for the threat of lightning," said Capt. William Whisel, 30th Operations Support Squadron weather flight commander. "There are nine rules collectively called the Lightning Launch-Commit Criteria which we, here at Vandenberg, evaluate for every launch. The first and simplest of these rules states that a launch operator must wait 30 minutes to launch a rocket after any type of lightning occurs within 10 nautical miles of the flightpath. Other rules are more complicated and force the Launch Weather Officer to dive deeply into meteorological interrogations and reasoning."

The weather flight monitors a multitude of factors gathered from dozens of sources, which are then processed by Vandenberg experts to form forecasts.

"In all, there are at least 23 different weather elements we monitor and if any one of these elements does not meet acceptable parameters, then the LWO calls the range RED for weather," said Whisel. "Since 1988, we have performed 317 operations, with 82 delayed or scrubbed due to weather. The majority of the time we have scrubbed due to upper-level wind shear, with downrange weather conditions coming in second. Simply put, wind-shear is radical changes in wind speeds or direction."

Some of the factors monitored are unseen but can have devastating effects on the satellite.

"For example, we monitor protons streaming from the sun and will notify a user if concentrations get too high," said Whisel. "A user or spacecraft vendor may delay a launch because now they have to check to ensure their satellite has not suffered a corrupted memory bit."

Although the weather flight gathers data from the 557th Weather Wing, the National Weather Service, the Navy, the Joint Space Operations Center to name a few, the instruments relied upon most heavily are from Vandenberg.

"We have our own Doppler weather radar that we use to interrogate for precipitation," said Whisel. "We also release weather balloons which transmit back the temperature and dew point as the balloon ascends from the surface."

While the data gathered from the weather balloons at Vandenberg directly influences each launch, the information is also sent to the National Oceanic and Atmospheric Administration database.

"We release two balloons per day, seven days per week," said William Shmeiser, 30th Operations Support Squadron weather systems director and senior meteorologist. "The data we receive from the sounding goes directly into the NOAA database and is included in the national weather models and analysis you see on television every day. We are one of about 240 upper air observatories contributing to this database in the U.S. We also release balloons for launch operations and other flight test support. Depending upon the mission we release from five to 15 balloons during a launch count, sometimes more if weather conditions demand."

The balloons themselves carry instrumentation that provides wind-speed and direction, atmospheric temperature and humidity every 100 feet from the surface of the earth to near the edge of space where the balloon finally bursts.

"This data allows us to determine maximum and minimum temperatures for the next day, the height of our inversion layer, at what altitude clouds have or will form, where the maximum winds aloft are, what time we will get our maximum surface winds, along with a host of other extremely useful weather forecasting information," said Shmeiser. "Normal daily balloons are flown to their burst altitude, somewhere between 90,000 and 120,000 feet. Balloons used for launch support are only tracked to the altitude desired by the launch agency or Range Safety."

Weather balloons remain one of the most important assets for gathering weather data for launches.

"Weather balloon operations are one of our most important tools for weather forecasting as well as for launch safety and launch operations," said Shmeiser. "The data collected during a launch operation is used to calculate where any debris or toxic plumes will go if there is an in-flight accident, and also is used to determine launch vehicle steering and load calculations. Our balloon data is also crucial to supporting the National Weather Service in their Fire Weather Forecasts, which directly supports fire fighters during wild fire emergencies. Upper air balloon support is critical to Vandenberg's launch mission as well as being a huge part of daily weather forecasting; not only on Vandenberg but across the community and the nation."