HURRICANE INTERCEPT

The simulation shows a blue circle for Hurricane Alberto (August 2000) and two balloon trajectories. The blue trajectory is an uncontrolled balloon. The red trajectory is a controlled trajectory with 2 m/s of trajectory control authority. The simulation shows has 1 frame every 4 hours. Real winds from UKMO are used in this simulation.

This simulation shows the potential importance of a Ballon Guidance System for monitoring hurricane activity.

STRING OF PEARLS

These two simulations show one potential balloon network performing a Hurricane Intercept Mission. The network of 20 balloons is arranged in a "String of Pearls" around the equator. When hurricane Alberto forms (August 2000), the network resources are mobilized to intercept and observe the hurricane. The network of balloons looks ahead to anticipate the hurricane ground track. The simulations show 1 frame every 4 hours, and tails on the balloon trajectories in the first simulation are 12 hours long. In the second simulation, the yellow circles represent the locus of points that emit to the balloons with an elevation angle of 2 degrees or more, and the green areas indicate overlap.

These simulations use real weather from the time of the hurricane to calculate the trajectories of the balloons. A realistic model of a StratoSail Ballon Guidance System (BGS) is used to adjust the trajectories of the stratospheric platforms.

These simulations demonstrate the potential importance of a Ballon Guidance System for monitoring hurricane activity.

RECONNAISSANCE APPLICATION

This shows a simulation of the use of stratospheric satellite platforms to achieve reconnaissance objectives. There are 100 platforms arranged along two latitude bands. Outside the magenta circle, the platforms are commanded to maintain 37° N latitude or 23° N latitude. Within the circle, the platforms use "look ahead" trajectory simulations to overfly a point at 34.5° N latitude and 69.2° E longitude.

This example summer simulation runs for 15 days from 15 June 2000 to 30 June 2000. The position of each stratospheric platform is represented by a red dot. Yellow circles represent the locus of points that emit to the balloons with an elevation angle of 2 degrees or more. The green areas indicate overlap. Each frame of the simulation represents 4 hours of the evolution of the network.

MOVE TO EQUATOR

This simulation shows the trajectories of 100 balloons with 5 m/s velocity bias toward the equator.

This simulation demonstrates that 5 m/s trajectory control is sufficient to provide significant alteration of the geometry of the global balloon constellation. The trick, then, is to use available trajectory control capabilities in an intelligent manner to maintain a desired constellation geometry objective.

CONSTELLATION MANAGEMENT--MOVE TO POLES

This simulation shows the trajectories of 100 balloons with 2 m/s velocity bias toward the poles.

This simulation also demonstrates that 2 m/s trajectory control is sufficient to provide significant alteration of the geometry of the global balloon constellation. The trick, then, is to use available trajectory control capabilities in an intelligent manner to maintain a desired constellation geometry objective.

CONTROLLED UNIFORM CONSTELLATION

The simulation on this page shows that it is possible to control the geometry of a global constellation using an underactuated and bounded control system. We utilize the same initial network of 100 balloons, but we apply an algorithm called "Paired North-South Zonal Control," which is described as follows:

• Zones are defined as -90 to -45, -45 to 0, 0 to 45, 45 to 90 latitude.
• Define the target number of balloons in each zone as 15, 35, 35, and 15, respectively.
• Every four hours, count the number of balloons in each zone.
• If the actual number differs from the target, specify balloons to be moved from nearby zones, give them the appropriate control instructions, and remove them from paired North-South control.
• Continue moving these balloons that are under zonal control until the destination zone is reached.
• For those balloons not under zonal control and whose nearest neighbors are not under zonal control, apply paired north-south control.

For those balloons not under zonal control and whose nearest neighbors are not under zonal control, apply paired north-south control.

• Only apply control when a StratoSat is closer than 2000 km from its nearest neighbor
• The control direction (when applied) is either north or south, nothing else.
• If a StratoSat is north of it's nearest neighbor, it is commanded north.
• If a StratoSat is south of it's nearest neighbor, it is commanded south.
• Re-evaluate control for each StratoSat every 4 hours.

This movie goes for 120 days like the free-floating movie.

HEMISPHERICAL NETWORK

The simulation shows a hemispherical balloon network performing detailed Earth science data collection. There are 383 balloons in a network from +15° latitude to the North pole. The position of each balloon is represented by a red dot. Yellow circles represent the locus of points that emit to the balloons with an elevation angle of 2 degrees or more. The green areas indicate overlap. Each frame of the simulation represents 1 hour of the evolution of the network.

For each balloon, control actions are determined by algorithms that have been used to describe the motion of flocks of birds and schools of fish. Control is achieved by means of a StratoSail® Ballon Guidance System (BGS).

The movie on this web page is a 7-day excerpt from a longer 390-day simulation. In the longer simulation, coverage quality is maintained throughout the year.

DEMONSTRATION EARTH RADIATION BUDGET EXPERIMENT

The simulation on this page shows a potential mission scenario for a Demonstration Earth Radiation Budget Experiment (DERBE). In this scenario, a balloon carries radiometry instruments. Launch occurs at Palestine, Texas, the existing NASA Scientific Balloon Facility, thereby minimizing launch costs.

A StratoSail® guides the balloon southward to 15 deg. North. Later, the trajectory moves to 20 deg. North. The objective is to fly over the DOE's Atmospheric Radiation Measurement (ARM) Program's Cloud and Radiation Testbed (CART) site in Oklahoma.

For this simulation, launch occurs on 30 June 2000. The flight lasts 92 days and achieves four passes at 35 km over the ARM site. Stratospheric winds are provided by UKMO assimilations.

THORPEX APPLICATION

This is a simulation using stratospheric balloons to achieve THORpex objectives. THORpex is a loose acronym for "The Hemispheric Observing system Research and Predictability Experiment". This simulation demonstrates a possible targeting test mission scenario that takes advantage of trajectory control for observations. The goal is to obtain multiple dropsonde samples in regions of high sensitivity for 2- to 10-day weather forecasts in the western U.S. This region of high sensitivity is the Pacific Ocean in Northern Hemisphere winter.

In this simulation, the Red trajectory shows an uncontrolled balloon floating at 35 km. The Green trajectory represents a "simple control" balloon at 35 km whose trajectory is being controlled by a StratoSail® BGS at 20 km. The objective of the simple trajectory control algorithm for the Green balloon is to maintain 45°-north longitude at all times. Thus, if the balloon is south of 45°, the BGS pushes the balloon north if possible, and vice versa. The Blue trajectory shows a balloon at 35 km with the same 20-km StratoSail® BGS as the green balloon. However, the Blue balloon uses a sophisticated trajectory control algorithm. At various times throughout the flight, the Blue balloon is commanded to maintain latitude or to move toward or away from the center of an observed vortex. Control actions are taken based on the structure of the wind field at the time the control decision is made. No forecast information is utilized.

This simulation begins at November 1, 2000 and ends on March 1, 2001, 120 days in duration. Only 15 days of the trajectories (starting from December 1, 2000) are shown for clarity. The arrows on the trajectories indicate direction of travel and are spaced at 6-hour intervals to demonstrate locations of possible sonde drops. Real stratospheric winds from the time of the flight are used for calculating balloon trajectories.

The table below gives the number of sonde observations in the region of interest over the 120 days of simulation.

GDIN APPLICATION

This section shows a simulation using stratospheric balloons to achieve Global Disaster Information Network objectives. GDIN is the "Global Disaster Information Network," a voluntary, independent, self-sustaining, non-profit association of nations, organizations, and professionals, from all sectors of society including NGO's, Industry, Academia, Governments, and International Organizations with an interest in sharing disaster information. The aim of GDIN is to provide the right information, in the right format, to the right people, in time to make the right decisions.

In this simulation, we have a network of balloons operating between +/- 20 degrees latitude. The network adapts to disasters, mobilizing the assets of the network to provide observations of the event and to provide communications options to relief workers on the ground.

The network consists of 100 balloons floating at 35 km, each is labelled for identification. Winds are provided by UKMO assimilations, and the start time for the simulation is 2000-01-01T00:00:00 GMT. The simulations lasts 365 days, the command synchronization interval is 4 hours, and the integration time step is 1 hour. The position of each balloon is represented by a red dot. Yellow circles represent the locus of points that emit to the balloons with an elevation angle of 2 degrees or more. The green areas indicate overlap. Each frame of the simulation represents 4 hours of the evolution of the network.

The control forces for the balloons are provided by a StratoSail® Ballon Guidance System.