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Predict is an open-source, multi-user satellite tracking and orbital prediction program

predictlogo PREDICT is an open-source, multi-user satellite tracking and orbital prediction program written under the Linux operating system by John A. Magliacane, KD2BD. PREDICT is free software. Users may redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License or any later version.

PREDICT software is released in three forms:

* A version compatible with Linux or Unix operating systems (as well as some derivatives, such as Mac OS X),
* A version for DOS and DOS-based operating systems operating on 32-bit CPUs (80386s or better) that contains many, but not all the features and functionality of the Linux/Unix version.
* Bundled as part of an application-specific Linux distribution (Portable PREDICT Plus!) that includes a small suite of satellite communication applications in addition to PREDICT that can all be booted from a pair of floppy disks. (No permanent installation required.)


Download PREDICT

PREDICT may be downloaded through the following links:

Shortly after its initial release in late 1999, PREDICT was evaluated by the Linuxberg/Tucows web site, and received a rating of four out of five possible penguins/cows. A lot has happened since.

  • PREDICT has been adopted as a standard application in the Debian distribution of Linux.
  • PREDICT is included in the latest version of Slackware Linux.
  • PREDICT has been successfully ported to the Sharp Zaurus Linux-based PDA!
  • The use of PREDICT software is outlined in Infrastructure for Internet-Based Operations (PDF document) by James Cutler, Gregory Hutchins, Christopher Kitts, and Robert Twiggs of the Space Systems Development Laboratory, Stanford University. This paper was presented at the 14th annual Utah State University conference on small satellites.
  • Several important advantages to using PREDICT software for small satellite ground support are illustrated in Design of a Distributed Ground Support System for Small Satellites (PDF Documement) by Richard M. Barry and Dr. Pieter J. Bakkes of the University of Stellenbosch Electronic Systems Laboratory, South Africa. This paper was presented at the 15th annual AIAA/Utah State University Conference on Small Satellites in August 2001.
  • Reference is made to PREDICT in TU Sat 1: A Novel Communications and Scientific Satellite (PDF Document), written by members of the Physics Department at Taylor University, and presented at the 16th annual USU Conference on Small Satellites in 2002.
  • PREDICT has been used to determine the Data Communication Accuracy of the ARGO Floats located in the seas adjacent to Japan. The following PDF Document provides further details.
  • The adaptation of PREDICT's core functions in the development of specialized tracking applications is discussed in a paper entitled Development of an Ikonos Coverage Prediction Application (PDF Document), authored at the Department of Geodesy and Geomatics Engineering at the University of New Brunswick, and the Department of Industrial Engineering at Dalhousie University.
  • PREDICT software was selected for use at Aalborg University's Institute of Electronic Systems (Denmark) for the operation of their SSETI-Express and AAUSAT-II automated satellite ground station. A detailed description of the development and operation of this system is available in PDF format.
  • Use of PREDICT is illustrated in Sources Sensitivity Simulator, Status Report (Postscript Document) written by Sonia Natale at the University of Geneva.
  • Use of PREDICT's internals is discussed in Orbit Optimization and Scattering Coefficient Analysis for the Proposed GLORIA System (PDF Document) by Bryan Welch, NASA / Glenn Research Center.
  • Use of PREDICT is cited in Routing in a Delay Tolerant Network (PDF Document) by Sushant Jain, Kevin Fall, and Rabin Patra.
  • Use of PREDICT is also cited in theses presented recently at Santa Clara University at both the Undergraduate and Graduate levels in Computer and Electrical Engineering.
  • eHam.net has several reviews of PREDICT.
  • Icewalkers.com has a page describing PREDICT software.
  • Linux2000 has a page describing the installation and use of PREDICT.
  • A description of the history and use of PREDICT software appeared in the July 2000 (Science and Engineering) issue of Linux Journal magazine.
  • John Heaton, G1YYH, has created several modifications to PREDICT Version 2.2.x to allow some additional features. Details and screenshots are available at his web site.
  • Fernand Lamberts, ON4LY, has developed several interesting graphical clients for PREDICT.
  • Christophe Mercier has developed JCP, a graphical Java client for PREDICT. Information on JCP, as well as a PREDICT user manual and installation guide in the French language is available at his web site.
  • PCRSAT, a PREDICT client application written by Vittorio Benvenuti, I3VFJ, allows operation of an ICOM PCR 1000 receiver in a satellite communication environment.
  • Iain Young, G7III, has also created some interesting PREDICT clients, including a telemetry decoder for the PCSAT, RAFT, and ANDE satellites.
  • Alexandru Csete's Groundstation Software Suite uses a derivative of PREDICT's source code for its satellite tracking functions.
  • Edson Pereira's PetitTrack satellite tracking software for the Sharp Zaurus SL-5000D and SL-5500 series Linux-based PDAs uses a derivative of PREDICT's source code for its tracking functions.
  • Ktrack by Luc Langehegermann, LX2GT, adopts some code and concepts from both PetitTrack and PREDICT. Luc has also developed a FODTRACK rotator interface utility for PREDICT.
  • Paul Williamson, KB5MU, has released Mac Vocalizer to enable PREDICT to run with speech announcements under Mac OS X.
  • Portable and modular coding has allowed users to successfully port PREDICT to operating systems, such as FreeBSD, Mac OS X, and Windows (using Cygwin-32).
  • Dana, N1OFZ, has created a web page that describes how to run PREDICT and GSAT successfully under Mac OS X.
  • David A. B. Johnson, G4DPZ, is actively developing a Satellite Tracking Web Service (websat) for the ESA/NASA/JAXA GENSO project that is based on code in PREDICT.
  • Andrew T. West has created PredictLib, a JavaScript satellite tracking library based on code contained in PREDICT.
  • Grace Peng has added an entry to her blog detailing her approach toward getting PREDICT to run on her MacBook Pro.
  • An interesting article entitled, Open Source Moved the Cheese, on an AMSAT discussion group describes the use of PREDICT as a low-cost, highly-capable alternative to hardware-specific approaches to satellite tracking.
  • Ralf Baechle, DO1GRB, has added gsat-1.1.0 plugin support for the Yaesu/Vertex Standard FT-847 transceiver. A source code patch and RPMs are available at: ftp.linux-mips.net.
  • new PREDICT version 2.2.3 has been released! This is a maintainance release that attempts to offer improved performance together with sustained compatibility with the latest versions of xplanet and gcc.

Predicting Satellite Passes

Orbital predictions are useful for determining in advance when a satellite is expected to come within range of a ground station. They can also be used to look back to previous passes to help to confirm or identify past observations.

PREDICT includes two orbital prediction modes to predict any pass above a ground station (main menu option [P]), or list only those passes that might be visible to a ground station through optical means (main menu option [V]). In either mode, the user is asked to select a satellite of interest from a menu, and then asked to enter the date and time (in UTC) at which prediction calculations should start. Orbital calculations are started and prediction information is then displayed on the screen.

select a satellite


The date and time in UTC, along with the satellite's elevation above ground, azimuth heading, modulo 256 orbital phase, sub-satellite point latitude and longitude, slant range between the ground station and the satellite, and the satellite's orbit number are all displayed. An asterisk (*) displayed to the right of the orbit number means the satellite is in sunlight at the date and time listed on the line. A plus symbol (+) means the satellite is in sunlight while the ground station is under the cover of darkness at the time and date listed. Under good viewing conditions, large satellites such as the International Space Station, and the US Space Shuttles are visible to the naked eye. If no symbol appears to the right of the orbit number, then the satellite is in the Earth's shadow at the time and date listed, and is not receiving any illumination from the sun.

Selecting [V] from PREDICT's main menu will permit a ground station to only predict passes for satellites that are potentially visible through optical means. Since all other passes are filtered out in this mode, and since some satellites may never arrive over a ground station when optical viewing conditions are possible, the program provides the option of breaking out of visual orbital prediction mode by pressing the [ESC]ape key as calculations are made. A prompt is displayed at the bottom of the screen to alert the user of this option.

In either orbital prediction mode, predictions will not be attempted for satellites that can never rise above the ground station's horizon, or for satellites in geostationary orbits. If a satellite is in range at the starting date and time specified, PREDICT will adjust the starting date back in time until the point of AOS so that the prediction screen displays the first pass in its entirety from start to finish.

Single Satellite Tracking Mode

In addition to predicting satellite passes, PREDICT allows satellites to be tracked individually in real-time using PREDICT's Single Satellite Tracking Mode (main menu option [T]), or simultaneously as a group of 24 using the program's Multi-Satellite Tracking Mode (main menu option [M]). The positions of the Sun and Moon are also displayed when tracking satellites in real-time.

Selecting option [T] from PREDICT's main menu places the program in Single Satellite Tracking Mode. The user will be prompted to select the satellite of interest, after which a screen will appear and display tracking positions for the satellite selected.

single tracking mode

In Single Satellite Tracking Mode, a wealth of real-time satellite data is provided by PREDICT. If the satellite contains an active communications downlink, uplink, or two-way communications transponder, then Doppler-corrected uplink and downlink frequencies, path loss, propagation delay, and echo are displayed. It is also possible to tune across the transponder's passband using certain keystrokes to locate a specific uplink or downlink frequency within the satellite's transponder. This makes it possible to determine the appropriate uplink frequency to match a desired downlink frequency (or vice-versa). PREDICT supports a number of transponders per satellite, including linear (both inverting and non-inverting), digital (Pacsat), and bent-pipe (FM). Also new to version 2.2.x is the determination of antenna squint angle and solar eclipse depth.

If a soundcard is present in your machine and the Single Satellite Tracking Mode is invoked with an uppercase 'T' rather than a lowercase 't', PREDICT will make periodic voice announcements stating the satellite's tracking coordinates in real-time. Announcements such as:

"This is PREDICT. Satellite is at fifty six degrees azimuth and forty five degrees elevation, and is approaching. Spacecraft is currently visible."

are made at intervals that are a function of how quickly the satellite is moving across the sky. Announcements can occur as frequently as every 50 seconds for satellites in low earth orbits such as the International Space Station (370 km), or as infrequently as every 8 minutes for satellites in very high orbits, such as the GE-2 geostationary satellite (35780 km). Voice announcements are performed as background processes so as not to interfere with tracking calculations as the announcements are made. Announcements can be forced at any time by pressing the 'T' key in Single Satellite Tracking Mode. Alarms are sounded at the precise moment when satellites enter into sunlight or into eclipse.

Solar Illumination Predictions

PREDICT even makes it possible to determine how much solar illumination a particular satellite will receive over the course of a day. This information is especially valuable to spacecraft designers and satellite groundstation controllers who must monitor spacecraft power budgets or thermal conditions on-board their spacecraft due to sunlight and eclipse periods. It can even be used to predict the optimum times for astronauts to perform extra-vehicular activities in space.

solar predictions

Multi-Satellite Tracking Mode

Selecting [M] from PREDICT's main menu places the program in a real-time multi-satellite tracking mode. In this mode, all 24 satellites in the program's database are tracked simultaneously along with the positions of the Sun and Moon. Tracking data for the satellites is displayed in two columns of 12 satellites each. The name, azimuth heading, elevation, sub-satellite point latitude (in degrees North) and longitude (in degrees West) positions are provided, along with the slant range (in kilometers), and the slant range distance between the satellite and the ground station (also in kilometers).

A letter displayed to the right of the slant range indicates the satellite's sunlight and eclipse conditions. If the satellite is experiencing an eclipse period, an N is displayed. If the satellite is in sunlight and the ground station is under the cover of darkness, a V is displayed to indicate the possibility that the satellite is visible under the current conditions. If the satellite is in sunlight while conditions at the ground station do not allow the satellite to be seen, a D is displayed. Satellites in range of the ground station are displayed in BOLD lettering. The AOS dates and times for the next three satellites predicted to come into range are displayed on the bottom of the screen between the tracking coordinates of the Sun and Moon. Predictions are not made for satellites in geostationary orbits or for satellites so low in inclination and/or altitude that they can never rise above the horizon of the ground station.

multitracking mode

Solar and Lunar Orbital Predictions

In addition to making orbital predictions of spacecraft, PREDICT can also predict transits of the Sun and the Moon. When making solar and lunar orbital predictions, PREDICT provides azimuth and elevation headings, the right ascension, declination, Greenwich Hour Angle (GHA), radial velocity, and normalized distance (range) to the Sun or Moon.

solar predictions

lunar predictions

The Declination and Greenwich Hour Angles correspond to the latitude and longitude of the object's sub-satellite point above the Earth's surface. The radial velocity corresponds to the speed and direction the object is traveling toward (+) or away (-) from the ground station, and is expressed in meters per second. When the radial distance of the Moon is close to zero, the amount of Doppler shift experienced in Moon bounce (EME) communications is minimal. The normalized distance corresponds to the object's actual distance to the ground station divided its average distance. In practice, the normalized distance can range from about 0.945 to 1.055 for the Moon, and about 0.983 to 1.017 for the Sun.

EME Support

Included with PREDICT is a utility called MoonTracker. MoonTracker supports moonbounce (EME) communications by calculating the position of the Moon, and sending appropriate control signals to an AZ/EL antenna rotator to track the Moon as it crosses the sky. Once invoked, MoonTracker spawns itself as background process, and continues to run until terminated by a kill signal. If the Moon is not above the horizon when MoonTracker is invoked, MoonTracker goes to "sleep" until the predicted time of Moon rise.

Client Applications

The Linux version of PREDICT includes networking code to permit its use as a socket-based server, allowing it to supply real-time tracking and orbital prediction information to client applications using the UDP communications protocol. A number of excellent client applications have been developed thus far for use with PREDICT, and more are on the way.

map program

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earthtrack globe

earthtrack zoom

The graphical client applications pictured above are included as part of the Linux version of PREDICT.

pb/pg screen

The latest version of PB/PG (a Pacsat communication suite) for Linux written by Bent Bagger, OZ6BL polls PREDICT for live tracking data, and displays the information in the center of PB's main screen.

source: About.com Linux

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About Hugo Repetto

Ubuntu is a Linux distribution that offers an operating system predominantly focused on desktop computers but also provides support for servers. Based on Debian GNU / Linux, Ubuntu focuses on ease of use, freedom in usage restriction, regular releases (every 6 months) and ease of installation.
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