[Introduction] [Operations] [Payload]

Introduction

tbex_logoTBEx, the Tandem Beacon Experiment (TBEx), consists of a tandem pair of CubeSats, each carrying tri-frequency radio beacons, in near identical, low inclination orbits and a cluster of diagnostic sensors on five islands in the Central Pacific sector. The science objectives and goals of TBEx are to study how the dynamics and processes in the troposphere can act to cause variability in the behavior of the upper atmosphere and ionosphere. TBEx was developed by SRI International and MXL with funding from NASA.

Status

  • 26 June 21:50 – No decoded beacons from the sats.  TBEx-A appears to have a signal but it is odd looking, a continuous wave transmission with some strong side lobes.  TBEx-B is quiet.
  • 25 June 10:50 AM – We are working through data and tracking now to see if TBEx signals have been received.  Our first chance to hear TBEx in Ann Arbor is tonight.
  • 25 June 4:30 AM – Launch was a success  and deployment was good!  Be sure to check online for launch photos.  Amazing.

Operations

Launch was successful!  Both TBEx satellites were deployed by the SpaceX Falcon Heavy.  The deployment times were 25 June 2019 07:13:52 and 07:08:47.

TBEx-A and TBEx-B should be on two frequencies given below.  Transmissions will initially be at 9600 bps / GMSK.  Data will be encapsulated in AX.25 UI Frames.

  • TBEx-A @ 437.485 MHz
  • TBEx-B @ 437.535 MHz

Each spacecraft has two beacons that are described online a Google Sheet and two json files, beacon 1 and beacon 2.  The beacon period is 10 seconds, nominally.

The initial TLEs are found below.  Although we have labeled the TLEs, we are not sure which satellite will be which TLE set.

NOTE, these TLEs do NOT have the 3 hour delay.  We’re away now and working on new TLE and tracking info.

TBEX-A
1 99999U          19176.14583333 -.00000000  00000-0  00000-0 0 00003
2 99999 028.5984 142.0410 0394051 105.4782 326.5543 14.97382750000019
TBEX-B
1 99999U          19176.14583333  .00000000  00000-0  00000-0 0 00002
2 99999 028.5867 140.7723 0394590 105.0870 326.8044 14.98003902000012

Payload

Each satellite has a tri-frequency transmitter.  The three frequencies are phase locked onboard the satellite.  As they pass through ionospheric disturbances, plasma bubbles, the phase of each transmission is affected proportionally to amount of plasma and the frequency.   Comparing the phase differences of the transmissions received by ground receivers, properties of the plasma can be inferred.  Payload transmissions will be commanded periodically during the mission.  Frequencies are given below.

  • TBEx-A: 150.012 MHz, 400.032 MHz, 1066.7520 MHz
  • TBEx-B: 149.988 MHz, 399.968 MHz, 1066.5813 MHz

Note, only the 150 and 400 MHz frequencies will be used for payload operations.

Contact Information

If you have any questions or comments, please reach out to our team below.

James W. Cutler, KF6RFX
Ph: 734-615-7238
jwcutler@umich.edu