A project data dictionary contains information required to make the data independently useable to a wide community. For ISTP the Common Data Format (CDF), chosen as the data exchange format for key parameter and event data, carries much (but not all) of the data dictionary information using a set of standard global attributes describing the overall CDF content and a set of standard attributes for each variable in the CDF. The variable attributes contain descriptions, data types, minimum and maximum values, labels, units, time tags, and if required, dependencies, uncertainties, and offsets. However there is little consistency in variable names nor in the descriptions that are tied to each variable, to help other users of the data find and use the variables of interest. We have extended the ISTP project data dictionary to include dictionary keywords that identify variables as being a certain type such as time or magnetic_field regardless of the naming convention adopted by the investigators. Each variable in a CDF has defined dictionary keywords (class and subclass) that are stored in its associated DICT_KEY attribute.
We provide a standard set of class keywords that include ‘sensor (science)’ and ‘supporting’ class words and their meanings, to be used to categorize the data variables of primary interest to investigators, among the several ISTP satellites and experiments. ISTP class keywords will be restricted to the approved values shown below. Sets of subclass keywords, with each set used to modify one of the class keywords, are also adopted and listed with the associated information below. Lists of common subclass keywords, valid for any variable, can also be found below.
Sensor Words Supporting Words anisotropy angle current energy density flag electric_field frequency magnetic_field label particle_flux number photon_flux ratio position significance potential source power species pressure time temperature uncertainty velocity wavelength
The dictionary keywords and definitions (along with the other global and variable attributes) comprise the primary content of the ISTP project data dictionary. The class keywords were selected to be, as much as possible, a complete and orthogonal set. In the realm of space physics there are three broad classes of sensor data words: electric and magnetic field (DC values for vectors, AC values for power spectra), particle distributions (e.g., densities, flow speeds, flow direction angles, thermal speeds, temperatures, anisotropy, fluxes), images (e.g., remote sensing of the aurora, ionosphere and sun at various wavelength ranges measuring e.g., electromagnetic waves, temperatures, pressures). In addition, there are time words, orbit/attitude words, and flags of various types (e.g.,instrument mode). We choose the measured quantities such as magnetic_field, density, temperature, to be the sensor (science) class keywords that are of primary science interest. Supporting keywords are of secondary science interest such as the energy or time at which a measurement was made, or the label or flag associated with a measured quantity. The sensor (science) class words are listed separately from the supporting class words below. It is envisioned that the usage of the sensor (science) and supporting class keywords will be different. Sensor Words make up a short, standard list that enables automated searching for data of interest at a fairly high level. Supporting Words are at a lower level of interest, but may still be used for some types of searches. In the CDF model every variable must have one and only one class keyword defined, but may have any number of subclass keywords defined.
ANGLE The geometric figure formed by two lines diverging from a point or two planes diverging from a common line or the space between two such lines or surfaces.
Subclass Words: antenna elevation pitch aspect fov pointing axis geometric polar azimuth inclination rotation phase sectorReturn to list of class keywords
ANISOTROPY The variation of physical properties with direction, usually expressed as a ratio.
Subclass Words: parallelReturn to list of class keywords
CURRENT The rate of flow of electricity.
Subclass Words: Hall primary load secondaryReturn to list of class keywords
DENSITY The mass per unit volume of a substance, or the number of items per unit volume.
Subclass Words: partial mass numberReturn to list of class keywords
ELECTRIC_FIELD The space surrounding an electric charge within which it is capable of exerting a perceptible force on another electric charge. The strength of an electric field at a given point is given in terms of the force exerted by the field on unit charge at that point.
Subclass Words: AC calibration amplitude DC angle potential antennaReturn to list of class keywords
ENERGY The property of a system that is a measure of its capacity for doing work.
Subclass Words: band channel incident reflectedReturn to list of class keywords
FLAG An entity that signals the occurance of an event, or that indicates a particular status of a spacecraft or instrument or software program. The flag can be a number, letter, or word, and may have any of a variety of encoded meanings.
Subclass Words: number post_gap quality statusReturn to list of class keywords
FREQUENCY The number of cycles completed by a periodic function in unit time.
Subclass Words: band channelReturn to list of class keywords
LABEL A term or phrase attached by way of classification or characterization.
Subclass Words: [All other class words are also possible sub-class words] alias name(s) sourceReturn to list of class keywords
MAGNETIC_FIELD The field of force surrounding a magnetic pole or a current flowing through a conductor, in which there is a magnetic flux.
Subclass Words: AC calibration amplitude DC angle potential antennaReturn to list of class keywords
NUMBER A symbol or word, or a group of either of these, showing how many or what place in a sequence.
Subclass Words: direction frame target event image telescope exposure mode filter sequenceReturn to list of class keywords
PARTICLE_FLUX The number of particles passing through a specified area or volume in a specified time interval (and possibly in a specified energy range or in a specified range of directions).
Subclass Words: differential number rate directional omni-directional sample integral parallel spectral mass perpendicular thermalReturn to list of class keywords
PHOTON_FLUX The number of photons passing through a specified area or volume in a specified time interval (and possibly in a specified energy or wavelength range or in a specified range of directions).
Subclass Words: brightness integral differential incident directional omni-directional filtered reflectedReturn to list of class keywords
POSITION A location, distance, or direction with respect to some particular reference. The reference can be moving or fixed, such as the geographic coordinate system or a spacecraft body.
Subclass Words: altitude distance radial angle elevation range antenna height RA attitude horizontal row azimuth inclination surface column latitude target declination longitude vertical direction projectionReturn to list of class keywords
POTENTIAL Electrostatic, magnetostatic, or gravitational potential, at a point in the field: the work done in bringing unit positive charge, unit positive pole, or unit mass respectively from infinity (i.e., a place infinitely distant from the causes of the field) to the point.
Subclass Words: antenna Hall bias magnetic electric polar_cap gravity surfaceReturn to list of class keywords
POWER The rate at which energy is expended or work is done.
Subclass Words: amplitude electric radiant antenna emission reflected bandwidth field spectral calibration flux transmittance density poyntingReturn to list of class keywords
PRESSURE Force per unit area.
Subclass Words: atmosphere magnetic derived solar dynamic surfaceReturn to list of class keywords
RATIO The quotient of one quantity divided by another of the same kind, and usually expressed as a fraction.
Subclass Words: albedo electric_field power beta energy pressure anisotropy particle_flux temperature current photon_flux velocity density magnetic_field spectralReturn to list of class keywords
Subclass Words: correlationReturn to list of class keywords
SOURCE The origin (mission, spacecraft, instrument, ground observatory, or other observing platform) of the data in question.
Subclass Words: experiment ground-based campaign investigationReturn to list of class keywords
SPECIES The identity of a particle or class of particles in detail, such as common name, chemical name, mass, charge state, atomic number, atomic weight, degree of ionization, mass per charge, etc.
Subclass Words: electron oxygen ion Z>3 proton neutral helium particle nitrogen dustReturn to list of class keywords
TEMPERATURE The degree or intensity of heat or cold as measured on a thermometric scale. Also the equivalent temperature corresponding to the energy of thermal motion of plasma particles, or the equivalent temperature as computed in radio measurements.
Subclass Words: characteristic parallel isotropic perpendicular operational thresholdReturn to list of class keywords
TIME The period between two events or measurements; a measurable interval, usually between a fixed reference (instant of time) such as 0 AD and the subject event or measurement.
Subclass Words: bin GMT minute clock hour PB5 cycle interval reference date Julian relative elapsed local second epoch magnetic spacecraft event millisecond UTReturn to list of class keywords
UNCERTAINTY An estimate of the lack of precision in an observed or calculated value.
Subclass Words: [All other class words are also possible sub-class words] percentReturn to list of class keywords
VELOCITY The rate of increase of distance traversed by a body in a particular direction (linear velocity) or the rate at which a body rotates about an axis (angular velocity). Speed is similarly defined with the omission of reference to direction.
Subclass Words: doppler horizontal speed drift phase thermal group rotation verticalReturn to list of class keywords
WAVELENGTH The distance from a particular point of a wave to that same point in the next oscillation cycle of the wave. Also a range of wavelengths, such as infra-red, visible, radio, x-ray.
Subclass Words: radio band primary IR bin scan visible channel resolution UV characteristic x-ray filter gamma ray nominalReturn to list of class keywords
The following lists of words are valid for more than one class word. Note that some species and wavelength subclass keywords are also considered to be common because they can be used in conjuction with several of the class words.
GENERAL Subclass Words: absolute instrument mean average interval offset center maximum spacecraft component measured vector derived minimum total
COORDINATE SYSTEM Subclass Words: cartesian GSM geographic HDZ geomagnetic HGI GCI NEV GSE polar SOURCE Subclass Words: electron oxygen ion Z>3 proton neutral helium particle nitrogen dust WAVELENGTH Subclass Words: radio IR visible UV x-ray gamma rayReturn to top of Document
Source Exp Variable Value of DICT_KEY All All Epoch time>Epoch_center_range IMP 8 MAG Time_PB5 time>PB5_center_range IMP 8 MAG B_GSE_c magnetic_field>GSE_cartesian_vector IMP 8 MAG B_GSM_p magnetic_field>GSM_polar_vector IMP 8 MAG Rad_dist position>radial_distance IMP 8 MAG SC_pos_se position>GSE_cartesian IMP 8 MAG Mode flag>mode IMP 8 MAG DQF flag>quality DARN GBAY vel velocity>drift_components DARN GBAY post_flag flag>post_gap DARN GBAY label_time label>time DARN GBAY label_unit label>unit Geotail EPIC IDiffI_I particle_flux>ion_differential Geotail EPIC IDiffI_I_Uncert uncertainty>ion_differential Geotail EPIC IDiffI_I_Energy energy>ion_center_channel Geotail EPIC IDiffI_I_Ch label>ion_energy_channel Geotail EPIC IDiffI_I_Eplus energy>ion_energy_plus Geotail EPIC IDiffI_I_Eminus energy>ion_energy_minusReturn to top of Document