Overview of the content

This lesson includes an overview and discussion of the tracking system: Iridium, OCCAMS and termination. This lesson includes an overview of Global Navigation Satellite Systems, including GPS. 

NEW: Feb. 16, 2024 - Important technical bulletin on vents. RE: Corrective Action when OCCAMS, VENT and CUTDOWN XBEE3’s are not appearing to be on the same network setting and not functioning; Reprogramming the XBEE3’s PANID setting on OCCAMS, VENT and CUTDOWN

NEW FEB 24: The vent / cutdown / Iridium commanding technical session was hosted in February 2023
-Download the slide deck here from the NEBP Google Drive
-View the meeting recording here


NOTE :A new folder of engineering resources was posted 5/9/23 and includes

  • 3D print files: Cutdown, PiCam, RFD900, Vent
  • Ground station code (the folder contains a zipped file and the main .exe)
  • Raspberry Pi video system: Instruction manuals and Ubiquiti Radio Config files
  • RFD900

Learning objectives

After completing this lesson, students will be able to:

  • Explain how balloons are tracked through the Iridium network and tracking websites
  • Understand Iridium OCCAMS, Termination and Vent
  • Learn about the SPOT trackers (new video posted 5/17/23)


Iridium Control System

Iridium Control System (AHAC poster) - download from our NEBP Education Google Drive folder

  • The Iridium system is a modem that connects our custom PCB, called an Occams board, to the Iridium satellite network so we can communicate to our payloads via our ground station. This system connects to our other payloads on our string using the XBee radio frequency modules. These modules are also used as microcontrollers for other systems on our flights.


Iridium (TM) Satellite Tracker MODEL 9602-LP

The tracking Iridium Modem and XBEE3 Control payload collects the local GPS data from the GPS satellites and provides the connection to the Iridium Satellites that in turn connect through the Iridium Ground Stations for distribution over the internet to the Montana State University database.


9602-LP Product Information (from NAL Research - external site)

9602-LP User Guide (from NAL Research - external site)

9602-LP Quick Start Guide (from NAL Research - external site)



The OCCAMS unit communicates with the redundant cutdown system. There is a PCB mounted 2.4 Ghz antenna on the XBEE3 short range radio that is required to communicate with the OCCAMS unit. Care should be taken to make sure this is not near metal or other transmitters.

OCCAMS: Optimized Command and Control Aerial Management System

  • ​​Documentation for OCCAMS v9 or later and software versions 1-3 or later. Notes and troubleshooting will apply to previous versions but use your discretion. Differences in board design can be seen in each respective design section.​ Last update Dec. 15, 2022


  • schematic drawing [download from NEBP Google Drive] 



High Altitude Student Platform (HASP) 2021 Final Report [in NEBP Google Drive]

  • Montana Space Grant Consortium-Montana State University Student Team Lance Nichols, Tim Uhlenbruck, Josh Phillips, Andy Kirby Authors Lance Nichols, Tim Uhlenbruck Faculty Advisors Randal Larimer, PE, and Dr. Michael Walach Abstract There is growing interest within the university and light payload balloon community to utilize zero pressure or solar heated balloons to provide extended or long duration flight capability.


NEW 5/9/23: Vent files for download are here: A new folder of engineering resources was posted 5/9/23

Sept. 2023: UMD Vent (previously known as the Montana Modified Vent)

This folder contains all the info necessary to construct and operate the 'UMD Vent' (previously known as the 'Montana Modified Vent') - it basically has all the same electronics and functionality as the Montana Vent, except that venting is done with a flapper valve (rather than the plunger) and flight termination is accomplished using a marman-band like release mechanism. 

Sept. 2023:  Maryland-Montana Mash-up Vent

This folder contains all the files necessary for the Maryland-Montana Mash-up Vent -- part files, guide to 3D printed parts, and required part orders.

Direct link to instructional video

SPOT Tracker

In this YouTube video, Dr. James Flaten from the Minnesota Space Grant discusses using SPOT Trace GPS devices for tracking stratospheric ballooning missions.


Global Navigation Satellite Systems (GNSS) -- this presentation will help you become familiar with the design and operation of Global Navigation Satellite Systems (GNSS) especially the Global Positioning System (GPS) [Download from NEBP Google Drive]


RFD Iridium Payload Boxes

Files for the payload boxes: PDF and AutoCAD files for RFD Iridium Top, Bottom and Door [Download from NEBP Education Google Drive; posted 7/17/23]


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