PDS_VERSION_ID                  = PDS3    
DATA_SET_ID                     = "HP-SSA-DTWG-6-TRAJECTORY-V2.0"                                  
RECORD_TYPE                     = UNDEFINED                                   
PRODUCT_ID                      = "KAZEMINEJAD_PHD_THESIS"           
PRODUCT_CREATION_TIME           = 2006-07-10T12:00:00                  
^PDF_DOCUMENT                   = "KAZEMINEJAD_PHD_THESIS.PDF"                             
            
    OBJECT                      = PDF_DOCUMENT                              
      DOCUMENT_NAME             = "Methodology Development for the
                                   Reconstruction of the ESA Huygens Probe
                                   Entry and Descent Trajectory"                                 
      DOCUMENT_TOPIC_TYPE       = "INFORMATION NOTE"  
      INTERCHANGE_FORMAT        = BINARY                                       
      PUBLICATION_DATE          = 2005-01-01                                
      DOCUMENT_FORMAT           = "ADOBE PDF"                                     
      DESCRIPTION               = "The European Space Agency's (ESA) Huygens probe performed a successful entry
                                   and descent into Titan's atmosphere on January 14, 2005, and landed safely on the
                                   satellite's surface.
                                   A methodology was developed, implemented, and tested to reconstruct the Huygens
                                   probe trajectory from its various science and engineering measurements, which were
                                   performed during the probe's entry and descent to the surface of Titan, Saturn's
                                   largest moon. The probe trajectory reconstruction is an essential effort that has to
                                   be done as early as possible in the post-flight data analysis phase as it guarantees
                                   a correct and consistent interpretation of all the experiment data and furthermore
                                   provides a reference set of data for 'ground-truthing' orbiter remote sensing measurements.
                                   The entry trajectory is reconstructed from the measured probe aerodynamic drag
                                   force which also provides a means to derive the upper atmospheric properties like
                                   density, pressure, and temperature. The descent phase reconstruction is based upon
                                   a combination of various atmospheric measurements such as pressure, temperature,
                                   composition, speed of sound, and wind speed. A significant amount of effort was
                                   spent to outline and implement a least-squares trajectory estimation algorithm that
                                   provides a means to match the entry and descent trajectory portions in case of
                                   discontinuity.
                                   An extensive test campaign of the algorithm is presented which used the Huygens
                                   Synthetic Dataset (HSDS) developed by the Huygens Project Scientist Team at
                                   ESA/ESTEC as a test bed. This dataset comprises the simulated sensor output
                                   (and the corresponding measurement noise and uncertainty) of all the relevant probe
                                   instruments. The test campaign clearly showed that the proposed methodology is
                                   capable of utilizing all the relevant probe data, and will provide the best estimate
                                   of the probe trajectory once real instrument measurements from the actual probe
                                   mission are available.
                                   As a further test case using actual flight data the NASA Mars Pathfinder entry and
                                   descent trajectory and the space craft attitude was reconstructed from the 3-axis
                                   accelerometer measurements which are archived on the Planetary Data System. The
                                   results are consistent with previously published reconstruction efforts."         
    END_OBJECT                  = PDF_DOCUMENT                              
     
END