The Draconid Fluence Calculator (DFC) is a Microsoft Windows tool developed for mission planners and spacecraft operators to calculate the projected fluence and flux as a function of time and mass for the Draconid 2011 meteor outburst. These quantities can then be used by the project to evaluate the shower risk posed to their vehicle or instrument. It should be noted that the calculations are based on the current NASA Meteoroid Environment Office’s Draconid forecast; predictions by other groups or individuals are not included at this time.
The tool requires information about the specific spacecraft orbit, either in the form of a Two Line Element (TLE) set or a series of Cartesian state vectors in J2000 Earth Centered Inertial (equatorial plane) coordinates. The program is only applicable for spacecraft with apogees at geostationary altitude or lower, and should not be used for the calculation of fluxes for more than a day on either side of the Draconid peaks, which are predicted to occur somewhere between 18:00 and 20:00 UT on October 8 of 2011. Care should be taken when using TLEs, as the orbits of vehicles close to the Earth can change rapidly with time, with the general wisdom being that a TLE for a spacecraft in low Earth orbit does not yield good positions for more than a couple of weeks beyond its epoch. Use of such with an epoch months in advance of the Draconid outburst will not produce useful data. The “Input” section of the help file better describes input file format and selection.
Once the program has an initial orbit as defined by the TLE, or a set of state vectors, it will step through the chosen time interval in 1 minute steps, calculating the radiant visibility, flux of meteoroids, and array tilt angle (0 degrees pointing straight at the Sun) for a specified particle mass in grams. The program will track which locations in the orbit are exposed to the radiant, which ones have the radiant blocked by the Earth, and the time of exposure, along with several other quantities of interest. See the Outputs section of the Help file for a more detailed description.
After downloading, the user should unzip the files to a subdirectory (e.g., \DFC); this will also be the working directory, which will contain state vector, TLE, and output files.
Future releases will be made pending changes in the forecast and/or bug fixes/improvements.
10/06/2011 - Version 2.0 – bug fix to sub-satellite longitude calculation
Operating System: Windows NT/2000/XP/7
Hardware Requirements: 733 MHz Pentium III or faster, 50 Mbytes disk space, >512 Mbytes RAM.
Input Description: The tool requires information about the specific spacecraft orbit, either in the form of a Two Line Element (TLE) set or a series of Cartesian state vectors in J2000 Earth Centered Inertial (equatorial plane) coordinates.
Point of Contact:
Users are encouraged to report bugs or problems to:
Marshall Space Flight Center
Phone: (256) 544-0686