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Tropical Wind Energy Conversion and Reference Level (TWERLE)

NSSDCA ID: 1975-052A-01

Mission Name: Nimbus 6
Principal Investigator:Dr. Pierre Y. Julien


The goals of the Nimbus 6 Tropical Wind Energy Conversion And Reference Level Experiment (TWERLE) were closely associated with the objectives of the Global Atmospheric Research Program (GARP) and included (1) measuring upper atmospheric winds in the tropics, (2) studying the relative air motion along isobaric surfaces to determine the rate of conversion of atmospheric potential energy into kinetic energy, and (3) providing direct measurements of various meteorological parameters that served as reference points in adjusting indirect temperature soundings made from satellites. The experiment consisted of two basic components: (1) approximately 300 constant-level meteorological balloons to yield measurements of winds, temperature, and pressure in the tropics and at southern hemisphere midlatitudes at 150 mb (about 13.6-km altitude), and (2) the Nimbus 6 random access measurements system (RAMS) to provide data collection and location determinations from the balloons. The 3.5-m-diameter polyester-mylar balloons were equipped with a transmitter-oscillator, solar power supply, digitizer/modulator, and sensors. The sensors consisted of a radio altimeter having an accuracy of better than plus or minus 20 m, a bead thermistor monitoring the ambient air temperature to an accuracy of 0.5 deg C, and a pressure sensor measuring the 150-mb flight altitude to an accuracy of 0.5 mb. A magnetic cutdown device was used to eliminate any accidental overflights into regions of the Northern Hemisphere north of 20 deg N latitude. The RAMS merely detected each balloon signal (401.2 MHz) and extracted the carrier frequency, balloon identification, and sensor data. This information, along with time references, was stored in digital form for subsequent relay to a ground acquisition station. The balloon's position and velocity were derived from the relative motion between the platform and the satellite by measuring Doppler shifts in the carrier signal received from the balloon. TWERLE was capable of a location accuracy of 5 km and a platform velocity accuracy of 1 m/s. For more detailed information, see Section 9 in "The Nimbus 6 User's Guide" (TRF B23261). For information concerning TWERLE data, contact Dr. Paul R. Julian, NCAR, P.O. Box 3000, Boulder, Colorado 80303. In addition to the TWERLE balloon experiment, many other experiments used RAMS. These experiments used ocean buoys to measure oceanographic and atmospheric parameters. Information about experiments can be obtained from principal investigators listed as Nimbus RAMS Experiments in the User's Guide and "The Nimbus 6 Data Catalog" (TRF B26731), both available from NSSDC.

Alternate Names

  • Nimbus6/TWERLE

Facts in Brief

Mass: 12 kg
Power (avg): 17 W

Funding Agencies

  • NASA-Office of Space Science (United States)
  • NASA-Office of Space Science Applications (United States)


  • Earth Science: Atmospheric Dynamics

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Ms. Rhea L. TalleyOther InvestigatorSigma Data Services Corporation
Mr. William R. BandeenOther InvestigatorNASA Goddard Space Flight Center
Dr. William W. KelloggOther InvestigatorNational Center for Atmospheric Research
Dr. Verner E. SuomiOther InvestigatorUniversity of Wisconsin-Madison
Mr. Charles E. CoteOther InvestigatorNASA Goddard Space Flight
Mr. Charles R. LaughlinOther InvestigatorNASA Goddard Space Flight Center
Dr. Pierre Y. JulienPrincipal InvestigatorNational Center for Atmospheric Researchpierre@engr.colostate.exu
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