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<div id="contentwrapper"><div id="rightcontent"><div id="headimage"><img height="100" width="530" alt="National Space Science Data Center Header" src="/logo/nssdc_header.jpg"/></div><h1>Radio Science Experiment (GRE)</h1><p><strong>NSSDC ID:</strong> 1985-056A-11<br/><strong>Mission Name:</strong> Giotto<br/><strong>Principal Investigator:</strong> Prof. Peter Edenhofer<br/></p><div class="twocol"><div class="urone"><h2>Description</h2><p>
          The scientific objectives of this experiment were to determine both the columnar electron content of Comet Halley's ionosphere and the cometary mass fluence from atmospheric drag by using the radio signals from Giotto during the Halley encounter on 13--14 March 1986. The measurements of cometary electron content and mass fluence were inverted to derive the spatial distribution of the electron and mass (dust and gas) density within Halley's coma. This experiment was an occultation-type, remote-sensing experiment which relied on the propagation effects of electromagnetic waves. The experiment took measurements of the phase (Doppler) shifts of the downlink carrier signals both at S-band (2.3 GHz) and X-band (8.4 GHz) as a function of time during the Halley encounter.
          </p></div><div class="urtwo"><h2>Alternate Names</h2><ul><li>GRE</li></ul><h2>Funding Agency</h2><ul><li>European Space Agency (International)</li></ul><h2>Discipline</h2><ul><li>Planetary Science: Small Bodies</li></ul><h2>Additional Information</h2><ul><li><a href="spacecraftDisplay.do?id=1985-056A">Giotto</a></li><li><a href="datasetSearch.do?spacecraft=Giotto&amp;experiment=Radio Science Experiment (GRE)">Data collections from this experiment</a></li></ul><h2/><p>
          Questions or comments about this experiment can be directed to:
          <a href="mailto:David.R.Williams@nasa.gov?Subject=NMC Comment/Question: Radio Science Experiment (GRE) (1985-056A-11)">Dr. David R. Williams</a>.
          </p></div></div><div class="clear"> </div><h2>Personnel</h2><table cellspacing="0" class="datatab"><thead><tr><th>Name</th><th>Role</th><th>Original Affiliation</th><th>E-mail</th></tr></thead><tbody><tr><td>Prof. Peter Edenhofer</td><td>General Contact</td><td>Ruhr-Universitat Bochum</td><td>edh@hf.ruhr-uni-bochum.de</td></tr><tr class="odd"><td>Prof. H. Buschert</td><td>Co-Investigator</td><td>Ruhr-Universitat Bochum</td><td> </td></tr><tr><td>Dr. Herbert Porsche</td><td>Co-Investigator</td><td>Deutsche Forschungsenstalt fuer Luft-und Raumfahrt</td><td> </td></tr><tr class="odd"><td>Dr. Michael K. Bird</td><td>Co-Investigator</td><td>Universitat Bonn</td><td>mbird@astro.uni-bonn.de</td></tr><tr><td>Dr. Pasquale B. Esposito</td><td>Co-Investigator</td><td>NASA Jet Propulsion Laboratory</td><td>pesposit@pop.jpl.nasa.gov</td></tr><tr class="odd"><td>Dr. Hans E. Volland</td><td>Co-Investigator</td><td>Universitat Bonn</td><td>volland@astro.uni-bonn.de</td></tr></tbody></table><h2>Selected References</h2><p>Edenhofer, P., <em>et al.</em>,
      The Giotto radio-science experiment,
      In--The Giotto Mission--Its Scientific Investigations, ESA SP-1077, edited by R. Reinhard and B. Battrick, pp. 173-186, Mar. 1986.
      </p><p>Edenhofer, P., <em>et al.</em>,
      First results from the Giotto radio-science experiment,
      <em>Nature</em>, 321, No. 6067, 355-361, May 1986.
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        <li>NASA Official: <a href="mailto:Edwin.J.Grayzeck@nasa.gov">Dr. Ed Grayzeck</a></li>
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