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@prefix datacite: <> .
@prefix dcterms: <> .
@prefix xsd: <> .
@prefix dwc: <> .
@prefix gcis: <> .
@prefix cito: <> .
@prefix dcat: <> .
@prefix prov: <> .
@prefix skos: <> .
@prefix rdf: <> .
@prefix biro: <> .

   datacite:identifier "nasa-podaac-grace_gsm_l2_grav_gfz_rl05a";
   datacite:hasIdentifier [ a datacite:AlternateResourceIdentifier; rdf:value "GRACE_GSM_L2_GRAV_GFZ_RL05A" ] ;
   dcat:landingPage <>;
   dcterms:description "FOR EXPERT USE ONLY. The difference between RL05 and RL05a is the treatment of orbit parameters in the final processing step when gravity field parameters are estimated: orbit parameters are fixed in RL05 and free in RL05a. Further details and background has been presented at the GRACE Science Team Meeting 2013; the presentation is available in the meeting proceedings which can be found here: (session 'Introduction and GRACE SDS', file '06_Flechtner_GFZ_RL05.pdf'). This dataset contains estimates of Earths static field geopotential derived from the Gravity Recovery and Climate Experiment (GRACE) mission measurements, produced by the GeoForschungsZentrum (GFZ) at Postdam. The data are in spherical harmonics averaged over approximately a month. The primary objective of the GRACE mission is to obtain accurate estimates of the mean and time-variable components of the Earths gravity field variations. This objective is achieved by making continuous measurements of the change in distance between twin spacecraft, co-orbiting in about 500 km altitude, near circular, polar orbit, spaced approximately 200 km apart, using a microwave ranging system. In addition to these range change, the non-gravitional forces are measured on each satellite using a high accuracy electrostatic, room-temperature accelerometer. The satellite orientation and position (and timing) are precisely measured using twin star cameras and a GPS receiver, respectively. Spatial and temporal variations in the Earths gravity field affect the orbits (or trajectories) of the twin spacecraft differently. These differences are manifested as changes in the distance between the spacecraft, as they orbit the Earth. This change in distance is reflected in the time-of-flight of microwave signals transmitted and received nearly simultaneously between the two spacecraft. The change in this time of fight is continuously measured by tracking the phase of the microwave carrier signals. The so called dual-one-way range change measurements can be reconstructed from these phase measurements. This range change (or its numerically derived derivatives), along with other mission and ancillary data, is subsequently analyzed to extract the parameters of an Earth gravity field model."^^xsd:string;
## Dates of dataset release and access
   dcterms:issued "2013-12-17T22:02:30"^^xsd:dateTime;

## Spatial and temporal information:
dcterms:spatial [
    a dcterms:Location, gcis:SpatialExtent;
    gcis:northBoundLatitude "88"^^xsd:float;
    gcis:southBoundLatitude "-88"^^xsd:float;
    gcis:eastBoundLongitude "180"^^xsd:float;
    gcis:westBoundLongitude "-180"^^xsd:float;
  ] ;
dcterms:temporal [
    a dcterms:PeriodOfTime, gcis:TemporalExtent;
    gcis:startDate "2002-08-01T00:00:00"^^xsd:dateTime;
    ] ;

## Attributes and keywords

## Instrument Instances
   prov:wasAttributedTo <>;

   a gcis:Dataset .

## This entity was produced by an organization:     
   prov:qualifiedAttribution [
      a prov:Attribution;
      prov:agent <>;
      prov:hadRole <>;
      ] .

## Also known as:
   skos:altLabel "GRACE_GSM_L2_GRAV_GFZ_RL05A";
   gcis:hasURL "";
   skos:exactMatch <> .
   skos:altLabel "PODAAC-GRGSM-20GA5";
   gcis:hasURL "";
   skos:exactMatch <> .