A ModelOfOperationObjectProperty describes a relationship between a part of a model of operation and another part of a model of operation.
A ReceiveRate defines a range of transfer rates at which an endpoint can receive data through a link.
A SpaceWireLinkState relationship identifies a mechanism for enabling a SpaceWire link.
A SpaceWireRMAPAddressValidRange identifies a range of memory addresses in an endpoint that are accessible through the RMAP protocol.
A TransmitRate defines a range of transfer rates at which an endpoint can deliver data through a link.
A maxInclusive data property defines an included upper bound of a range of values.
A minInclusive data property defines an included lower bound of a range of values.
A modelOfOperationAttribute property describes a relation between a part of a model of operation and a specific type of data.
A protocolId identifies a communication protocol.
The data sheet language specifies the versions of documents that control the syntax and semantics of the SEDS instance in which they appear.
A DataTransferRateRange defines a range of data transfer rates.
Design parameters adjust the behavior of a component to suit the context in which it operates. The context includes the assembly of components in which the component operates. It also includes the standards of the agency that builds and operates the assembly of components. Often the assembly of components is a vehicle. Design parameters must be delivered to a component from the designers of the assembly in which it operates. For this reason, the description of design parameters takes the form of an interface to the component.
The Dictionary of Terms is the ontology in which this concept is defined. SANA publishes this ontology. This concept may be used in the "subject" semantic attribute of a meatadata value, to indicate that the version number is a version of the Dictionary of Terms.
Standard types of error control algorithms
Extensions to the enumerations in the seds.xsd file.
The manufacture topic in a model of producction identifies a device or software component by describing how it was made.
The manufacturer is the organization that constructed a device or software component.
The manufacturers model is a string assigned by a manufacturer to identify a kind of product that it makes.
A model of operation is a description of the parts of a component and the context in which the component operates. A model of operation may be expressed in a data modeling language, such as MOF or SysML, and then extracted into a set of OWL classes and relations. The OWL model of operation contains an individual in the ModelOfOperation class, called the anchor. The anchor has object relations to individuals in other classes that form a graph. A semantic attribute that corresponds to a referential class has for its value a string that describes a path through the graph starting from the name of the anchor and traversing relations by name to a set of target individuals. The meaning of the attribute is a relationship between the EDS object in which the attribute appears and target individuals in the model of operation.
A model of production describes the provenance of a device or software component.
A ParameterOpsType provides an element in which to describe the operational constraints on a parameter.
QUDV is an ontology that defines units of measure and quantity kinds. It is published by Object Management Group, so its version numbers follow the conventions of that group. The DoT uses QUDV for the subject matter that it covers.
A class derived from RefersToModel may be called a referential class, and shall have no individual members. A semantic attribute in the electronic data sheet schema that corresponds to a referential class shall have a range of values in "xsd:string". The prefix of the string shall be the name of an individual in the "ModelOfOperation" class or a derivative of that class. The remainder of the string shall be a path expression delimited by ".", which consists of alternating names of object relations and names of classes or individuals. The definition of a referential class shall relate the part of the electronic data sheet that bears the attribute to the individuals or classes in the ontology that are at the end of the path specified by the value of the attribute.
The version numbers for the schema and for the DoT shall have the form of three positive integers concatenated with period-characters, “.”. 1. The first integer shall be zero for the first version and incremented by 1 for versions that are not backward compatible with the previous version. 2. The second integer shall be zero for each first version that breaks compatibility and incremented by 1 for versions that extend the previous version while maintaining compatibility. 3. The third integer shall be zero for each first version that breaks compatibility or that extends compatibly, and incremented by 1 for versions that correct errors in previous versions without breaking compatibility and without extending compatibly. Example – 1.2.0
The schema governs the content of an Electronic Data Sheet. SANA publishes the schemas for electronic data sheets. This concept may be used in the "subject" semantic attribute of a metadata value of ConfigurationManagement in order to indicate that the value is a version number for the schema that governs the Electronic Data Sheet in which it appears.
A SemanticProperty is an enumeration of properties that describe the intended usage of data in a SOIS electronic data sheet.
A serial number is a string assigned by a manufacturer to identify a particular instance of a kind of product that it makes.
A SpaceWireLinkEnablement describes the mechanism to enable a SpaceWire link.
A SpaceWireLogicalAddressRange specifies the included bounds on a range of SpaceWire logical addresses.
A SpaceWireProtocol describes the parameters that constrain the content and sequencing of data sent and received through a SpaceWire link.
A SpaceWireSubnet is a model of operation of SpaceWire as a sub-network in SOIS. The attributes of this class and of associated classes define the SpaceWire configuration parameters.
A Subnet is a description of the parameters of a technology that implements the functions of the physical, datalink, and network layers of a standard OSI protocol stack in a SOIS protocol stack. The Subnet description provides a standard framework in which to specify the particular technology parameters for a device in a SOIS electronic data sheet.
The UnitsNotYetIntegratedIntoQUDV is a temporary category of discrete concept where the concepts that represent units not covered by QUDV conventions can reside until the QUDV conventions have been implemented.
A version is a string assigned by the manufacturer to identify a stage in the development of a kind of product that it makes. Some versions may be offered in a market, while others may be used only internally for experimental development.
This term indicates the handedness of a coordinate system.
The “coordinate type” term indicates how to interpret a semantic type that is an array of coordinates. The arrays to which the coordinate type applies may be interpreted as locations in a phase space, such as position and velocity vectors. For arrays that may be interpreted as transformation from one frame to another, such as quaternions and direction cosine matrices, the transformation type applies. The “coordinate type” term specifies a particular combination of the following terms: • coordinate system • array size • unit of measure • reference frame Some of the terms listed above may be incompletely determined by a “coordinate type” value, and so must be specified in an electronic data sheet with that “coordinate type” value when defining an item of data. Those terms above that are completely determined by a “coordinate type” value need not be specified with that value in an electronic data sheet. The definition of a value of the “coordinate type” term in the dictionary of terms must provide the information about the terms listed above. In an electronic data sheet this term is the “coordinateType” attribute of a data item. Use Cases: Interpret a semantic type that is an array of numbers.
Variables that represent a difference between values of measureable quantities are called “relative” variables. This term identifies the convention for computing the difference. In an electronic data sheet this term is the “differenceConvention” attribute of a data item. Use Cases: Specify that the change in speed reported by a single-axis accelerometer is the difference between the speed at the time of reporting and the speed at the time of the previous report.
The classes derived from this class represent enumerations that may be the range of a data item in an interface described by an electronic data sheet. The individuals in classes derived from this class are discrete concepts that are values in the range of an enumeration data item in an interface described by an electronic data sheet.
This concepts enumerates the states of health of a device.
The “interpretation” term identifies a broad class of data types to which an item of data belongs. In an electronic data sheet, this term is the “interpretation” attribute of a data item. Use Cases: Determine how to interpret the semantic type string for a data item. Distinguish an index from a count. Distinguish a transformation from a position.
An element bearning this semantic attribute is a member of the class in a standard or user-provided model of operation, named by the value of the attribute. Standard models of operation cannot efficiently represent the variety of details that may occur in a specific instrument. To address this difficulty, the parts of a standard model of operation, which are classes, can be interpreted as a skeletal model. Individuals in the classes of a standard model of operation can be defined in an electronic data sheet, and can be related to those classes by the referential attriibute "memberOf". This convention allows electronic data sheets to define a variety of operating models without needing a user-provided ontology, which would diminish their portability.
The purpose of a semantic type determines how to apply an instance of the type. A person may think that the purpose of a semantic type derives from its context of usage, for example, thinking that a parameter of a command must be a set-point. However, measured values that are not set-points may also be parameters of a command. Both set-points and measured values may appear in published data. The purpose may be clear for simple commands and telemetry that set a data item in a device; in those cases, the purpose attribute can be left implicit. In some housekeeping telemetry the distinction is not so clear; both set points and measurements may appear in the same relation; in those cases, the purpose attribute must be explicit on each data item. In an electronic data sheet this term is the “purpose” attribute of a data item. Use Cases: Distinguish a set-point from a measurement to be controlled. Distinguish a central value from a measured value. Distinguish an adjustment from a measurement
The “reference frame” term identifies the frame of reference in which a semantic type is relevant. The generic names of frames are employed here, such as “device” and “vehicle”; these generic names do not imply a specific coordinate system. For example, “ECI” is a value of this enumeration, while the more specific “J2000”, “TOD”, and “MOD” are reserved for the “coordinate type” enumeration. In an electronic data sheet this term is the “referenceFrame” attribute of a data item. Use Cases: Determine the frame in which a semantic type is represented, in order to determine what transformation is needed, if any, to represent the semantic type in a frame that is appropriate for an application. Determine the frame of reference that is input to a transformation of coordinates.
When a time stamp appears in a relation with other data items, it may be important to a designer of a control system to know how the time stamp relates to the age of the other data items in the relation. In an electronic data sheet this term is the timeRelation attribute of a time stamp data item. Use Cases: Enable a design of a control system to estimate the delay between measurement of a data value and the time when the control system obtains the data item.
The starTrackerOperatingMode enumerates the modes of operation of a star tracker.
The “status convention” describes how a data item represents the quality of function of a device. In an electronic data sheet, this term is the “statusConvention” attribute of a data item. Use Cases: Determine whether the data reported by a sensor can be trusted.
The subject property is a reference to a component of the system in which the data item using the subject property appears. The meaning is that the data item applies to the component. For example, if the purpose property of the data item is "measurement", then the data item is a measurement of the component referenced in the subject property.
The toCoordinateType identifies the coordinate type that results from a transformation from the coordinate system identified by the coordinateType.
The toFrame idenitifies the frame of reference that results from a transformation from the frame identified by the referenceFrame.
The “transformation type” term indicates how to interpret a semantic type that is an array of numbers. The arrays to which the transformation type applies may be interpreted as transformation from one frame to another, such as quaternions and direction cosine matrices. For arrays that may be interpreted as locations in a phase space, such as position and velocity vectors, the coordinate type applies. A coordinate type that is a vector may be treated as a transformation by adding it to other vectors, for example; such a transformation would be a called a translation. The “transformation type” term specifies a particular combination of the following terms: • coordinate system • array size • unit of measure • computation The definition of a value of the “transformation type” term must provide the information about the terms listed above. The “reference frame” and “to frame” must be specified with the transformation type in an electronic data sheet when defining an item of data. In an electronic data sheet this term is the “transformationType” attribute of a data item. Use Cases: Interpret the quaternion that is emitted by a star tracker.
The “DCM” value of the “transformation type” term specifies the following information for a semantic type: • coordinate system = rectangular • array size = (n, n), row-major order • unit of measure is not applicable • the transformation is computed by matrix multiplication The elements of the matrix are interpreted as direction cosines.
The design parameters are delivered to the component through dual in-line packaged switches.
The acronym ECEF consists of the initials of Earth-centered, Earth fixed. Data for Earth observation frequently refer to locations on the surface of the planet. This term identifies the frame that rotates with the Earth to describe semantic types that represent data about the surface of the earth. This reference frame must be accompanied by specification of coordinate type when used to describe a data item in an electronic data sheet. Use Cases: Specify the frame of latitude and longitude measurements. Specify an approximate frame of geosynchronous spacecraft.
The acronym ECI consists of the initials of Earth-centered, inertial. The inertial frame of the Earth is generally based on the positions of remote stellar objects. This reference frame is only approximately inertial, because of the acceleration of Earth to maintain its orbit. This reference frame must be accompanied by specification of coordinate type when used to describe a data item in an electronic data sheet. Use Cases: Specify the frame of the remote stars that form the basis for attitude measurement by a star tracker. Specify the location of a vehicle in interplanetary flight.
The International Celestial Reference Frame is heliocentric, with the origin at the barycenter of the solar system. The ICRF is the frame for the International Celestial Reference System.
The International Celestial Reference System has its origin at the barycenter of the solar system. The pole is defined by the International Astronomical Union models for precession and nutation. The origin of right ascensions is the same as J2000. • coordinate system = azimuth, right ascension • array size = 2 • unit of measure quantity kind = angle • reference frame = ICRF
The “J2000” value of the “coordinate type” term specifies the following information for a semantic type: • coordinate system = Cartesian • array size = 3 • unit of measure = length • reference frame = ECI The elements of the vector are interpreted as Cartesian coordinates. This approximately inertial coordinate frame has its origin at the center of the Earth. It is defined with the Earth's Mean Equator and Equinox at 12:00 Terrestrial Time on 1 January 2000. The x axis points toward the mean equinox corresponding to northern spring. The z axis points north along the earth’s spin axis. The y axis is 90 degrees east of the x axis in the plane of the equator, such that it forms a right-handed coordinate system. The “unit of measure” must be specified with this coordinate type. Use Cases: Specify that a semantic type is a vector with a coordinate system that corresponds to ECI J2000.
The “LLA” value of the “coordinate type” term specifies the following information for a semantic type: • coordinate system = latitude, longitude, altitude • array size = 3 • unit of measure = degree, degree, meter • reference frame = ECEF The elements of the vector are interpreted as spherical coordinates, and the two angle coordinates are treated as latitude and longitude; the radial coordinate is zero at the radius of Earth’s mean sea level. This coordinate system has its origin at the intersection of the prime meridian and the equator. Latitude is often marked north or south, instead of using negative angles. Similarly, angular distance around the equator is often marked as east or west. Use Cases: Specify the semantic type of a vector location of a building on Earth that is a target of surveillance.
The acronym LVLH consists of the initials of local vertical, local horizontal. This is the vehicle frame of an orbiter. The LVLH frame typically uses a Cartesian coordinate type oriented so that the x axis points in the direction of flight, the z axis points toward nadir, and the y axis points to the right in the viewpoint of a person looking in the direction of flight, to make a right-handed rectangular coordinate system. Use Cases: Specify the frame from which a surveillance satellite observes the Earth.
The “MOD” value of the “coordinate type” term specifies the following information for a semantic type: • coordinate system = Cartesian • array size = 3 • unit of measure = length • reference frame = ECI The elements of the vector are interpreted as Cartesian coordinates. This approximately inertial coordinate frame has its origin at the center of the Earth. It is defined with the Earth's mean equator and equinox at a particular date, assumed here to be the time of the measurement. The x axis points toward the mean equinox corresponding to northern spring. The z axis points north along the earth’s spin axis. The y axis is 90 degrees east of the x axis in the plane of the equator, such that it forms a right-handled coordinate system. The “unit of measure” must be specified with this coordinate type. Use Cases: Specify that a semantic type is a vector with a coordinate system that corresponds to ECI MOD at the time of measurement.
A SpWLogicalAddressRange defines a range of logical addresses that can be used to address an endpoint on a SpaceWire link. The syntax is low value followed by high value, separated by a colon. The values are unsigned integers that can fit in an octet.
A SpWProtocolId constrains the content and sequencing of data sent and received through a SpaceWire link. One protocol id should be specified per interface, and the the interface describes the content of data sent and received on a SpaceWire link. The state machine of the component that interacts across the interface describes the sequencing of data sent and received. The format of a protocol id is an unisgned integer that fits in an octet, or one of the standard protocol names in {RMAP, CPTP}.
A SpWRMAPAddressRange identifies a range of memory addresses in an endpoint that are accessible through the RMAP protocol. The format of this specification is a list of memory ranges separated by commas. Each memory range consists of a low value followed by a high value followed by a memory identifier followed by a spacewire RMAP write support code, with colons between. The values and the memory identifier are unsigned integers. The SpaceWire RMAP write support code is a string in {"ack", "ver"}.
A SpWReceiveRate defines a range of transfer rates at which an endpoint can receive data through a link. The syntax is low value followed by high value, separated by a colon. The values are integers, in units of Mbit/sec.
A SpWTransmitRate defines a range of transfer rates at which an endpoint can send data through a link. The syntax is low value followed by high value, separated by a colon. The values are integers, in units of Mbit/sec.
The “TOD” value of the “coordinate type” term specifies the following information for a semantic type: • coordinate system = Cartesian • array size = 3 • unit of measure = length • reference frame = ECI The elements of the vector are interpreted as Cartesian coordinates. This approximately inertial coordinate frame has its origin at the center of the Earth. It is defined with the Earth's true equator and equinox at a particular date, assumed here to be the time of the measurement. The x axis points toward the true equinox corresponding to northern spring. The z axis points north along the earth’s spin axis. The y axis is 90 degrees east of the x axis in the plane of the equator, such that it forms a right-handled coordinate system. The “unit of measure” must be specified with this coordinate type. Use Cases: Specify that a semantic type is a vector with a coordinate system that corresponds to ECI TOD at the time of measurement.
The “UPS” value of the “coordinate type” term specifies the following information for a semantic type: • coordinate system = latitude, longitude • array size = 2 • unit of measure = degree • reference frame = ECEF The elements of the vector are interpreted as universal polar stereographic coordinates. Use Cases: Specify that a semantic type is a vector location on Earth, with a coordinate system that corresponds to universal polar stereographic coordinates.
The “UTC” value of the “coordinate type” term specifies that a number is coordinated universal time as defined by the International Telecommunication Union and the International Astronomical Union. The abbreviation is a compromise between “coordinated universal time” and “temps universel coordonné”. Use Cases: Represent the time obtained from a global positioning system. Represent the time obtained from an atomic clock.
The “UTM” value of the “coordinate type” term specifies the following information for a semantic type: • coordinate system = latitude, longitude • array size = 2 • unit of measure = degree • reference frame = ECEF The elements of the vector are interpreted as universal transverse Mercator coordinates. Use Cases: Specify that a semantic type is a vector location on Earth, with a coordinate system that corresponds to universal transverse Mercator coordinates.
The "acquiring" relation to timestamp indicates that the timestamp is simultaneous with the acquisition of a datum.
A semantic type with purpose = action is a specific amount of action to be applied to the real world through an actuator. Use Case: Distinguish a torque to be applied to a reaction wheel from a stress measured by a strain gauge nearby.
The binary status convention indicates whether a device is functioning correctly or erroneously. The data item has the value 0 if no error is being detected, and it has the value 1 if an error is present. Typically, the binary representation of such a variable would be bit or unsigned integer. Use Cases: The SOIS accelerometer interface uses this convention to report device status.
A semantic type with purpose = calibration represents a number that is a measurement obtained through a calibration procedure. It is a value obtained specifically for each instance of a device. Use Cases: Distinguish an adjustment from a measurement.
Variables with this interpretation are the verb of a command.
The “comparison” term identifies the difference convention for variables without a specific absolute reference frame. Use Cases: Specify that the voltage reported by a voltage meter is a difference in potential without a reference ground.
The design parameters are delivered to the component through a configuration file.
The controller is activiely attempting to achieve it set point.
The design parameters are delivered to the component when its software is compiled, using constants, such as #define statements in c.
The “delta” term identifies a difference between the value of a variable at one time compared to the value at a prior time. For measurements, the prior time is the time that the variable was last reported, or since initialization. For commanded values, the prior time is the time of the current command. Use Cases: Identify the change in speed reported by an accelerometer. Identify the elapsed time since the last report of a measurement from a sensor. Specify the time during which a command parameter is valid.
Most measurements and actuations are made in the frame of the instrument. This term identifies that frame to describe semantic types that represent measurements or actuations in the frame of a device. Use Cases: Specify the frame of torque of a reaction wheel. Specify the frame of rotation in the transformation reported by a star tracker. Specify the frame of measurement of a coarse sun sensor.
Variables with this interpretation represent a difference between one physical quantity and another on the same scale.
The data managed by the command and data handling system of a vehicle often contains information about other objects, such as targets of surveillance or approaching vehicles. An identifier of the external object should appear in the same aggregation relation with this reference frame, or in the electronic data sheet description of a data item. Use Cases: Exchange position and attitude information with an approaching vehicle during docking. Distinguish the location of a ship at sea from the nadir point of an orbiter.
A fraction of maximum is a number in which the value 0 represents the minimum value of a scale, and the value 1 represents the maximum value of the scale. The minimum and maximum values of the scale must be explained separately.
The "generation" relation to timestamp indicates that the timestamp is simultaneous with the generation of a datum.
The “gradient” term identifies a difference computed as the ratio of a delta variable to a path variable. Such a variable is an average obtained by dividing the differences over the same reporting interval. Use Cases: Identify the rate of change of atmospheric density with altitude at a particular time and place.
This kind of reference names a ground station.
A device in good health is operating correctly, without no errors detected.
A severe health warning indicates that errors have been detected and reset is recommended.
A health warning indicates that some errors have been detected by reset is not required.
The controller is within the specified tolerance of its set point.
The design parameters are delivered to the component through jumpers.
The “LatLon” value of the “coordinate type” term specifies the following information for a semantic type: • coordinate system = latitude, longitude • array size = 2 • unit of measure = degree • reference frame = ECEF The elements of the vector are interpreted as spherical coordinates, but only the two angle coordinates are used; the radial coordinate is fixed at the mean radius of Earth. This coordinate system has its origin at the intersection of the prime meridian and the equator. Latitude is often marked north or south, instead of using negative angles. Similarly, angular distance around the equator is often marked as east or west. Both of these directional conventions must be specified if a device uses them; the term is “latlon convention”. Use Cases: Specify the semantic type of a vector location of a ship at sea on Earth.
A left-handed coordinate system has three dimensions, and the order of the presentation of positive values of the dimensions in a vector corresponds to the directions of thumb, index, and medius fingers of a human left hand.
A semantic type with purpose = measurement is a measurement of the real world obtained by a sensor. Use Cases: Distinguish a set-point from a measurement to be controlled. Distinguish a central value from a measured value. Distinguish an adjustment from a measurement.
Variables with this interpretation represent a mode of operation of a device.
When an instrument is attached to the structure of a spacecraft, there may be bracket that positions and orients the device relative to the vehicle. The mount reference frame is the reference frame associated with the face of the bracket, or associated with the face of mounting point on the vehicle structure when no bracket is present. In order to transform instrumentation measurements and actuations between device frame and vehicle frame, it is necessary to know the mounting frame as an intermediate step. Use Cases: Specify the frame in which a reaction wheel is mounted to the structure of a vehicle. Specify the frame in which a star tracker is mounted to the structure of a vehicle.
Variables with this interpretation are names of objects or variables in the management model of a system.
A semantic type with purpose = nominal is a number that is a non-specific central value over all instances of a device that result from a reproducible manufacturing process. Use Cases: Distinguish a central value from a measured value.
Variables with this interpretation define an orbit.
The “path” term identifies a difference between the value of a variable at one point on a path and the value at a prior point on the path. The path is the continuously changing location and orientation of the device frame for the variable relative to the reference frame for the variable. The prior point is the location at the time of the prior report or command. Use Cases: Identify the change in the Earth’s magnetic field reported by a magnetometer during the flight of the vehicle on which it is mounted.
Variables with this interpretation represent a position in phase space.
The quality fraction status convention indicates a fractional quality of service, with zero representing complete failure and 1 representing completely successful operation. The method of computing this value is an algorithm that varies from device to device, and is explained in natural language in an unstructured text field in an electronic data sheet. Use Cases: Specify the quality of data produced by a star tracker.
The “Quaternion” value of the “transformation type” term specifies the following information for a semantic type: • coordinate system = Cartesian. • array size = 4. • unit of measure is not applicable • the transformation is computed by conjugation The four coordinates are a scalar first, followed by three vector coordinates, corresponding to the orthogonal Cartesian coordinate axes x, y, and z, with the same chirality as the coordinate system. Chirality of the coordinate system must be specified in an electronic data sheet when using this term.
The “signalNoiseRatio” term indicates that a variable is a quotient of two quantities.
A right-handed coordinate system has three dimensions, and the order of the presentation of positive values of the dimensions in a vector corresponds to the directions of thumb, index, and medius fingers of a human right hand.
The “roll-pitch-yaw” value of the “transformation type” term specifies the following information for a semantic type: • coordinate system is Cartesian, right-handed • array size = 3 • unit of measure = degree • the transformation is computed by constructing a rotation based on the description below The three coordinates are a variant of Euler angles, based on the convention that the Cartesian coordinates of the vehicle frame are aligned with LVLH. The three coordinates are not distances in this coordinate system; rather they are rotation angles around the axes of the coordinate system. Roll is rotation around the direction of flight (x). Pitch is rotation around the y axis. Yaw is rotation around the z axis. All these rotations use the right-handed convention for sign.
The “rotation rate” value of the “transformation type” term specifies the following information for a semantic type: • coordinate system = Cartesian • array size = n • unit of measure = angle / time • the transformation is generally not computed, because this vector is often used directly as a measurement and as a set point for an attitude control system The vector represents the rate of rotation of the “to frame” relative to the “reference frame”. The elements of the vector are the angular rates around each axis of the reference frame. Chirality of the coordinate system must be specified in an electronic data sheet when using this term. Unit of measure for the rate must also be specified in an electronic data sheet when using this term.
Variables with this interpretation represent a region or subset of a device.
The "sending" relation to timestamp indicates that the timestamp is the time when the message that contains it was sent.
A semantic type with purpose = set-point is a value to be achieved by a control system, or a setting to be applied to a component. Use Cases: Distinguish a set-point from a measurement to be controlled.
The “sinceEpoch” term identifies the amount of time that has elapsed since a calendar epoch, so the data item that it describes is a date and time. Use Cases: Provide a time stamp on housekeeping data. Specify the time when an action should be performed.
The “sinceSync” term identifies the amount of time that has elapsed since the last synchronization signal. Use Cases: Identify the time at which a measurement was reported by a star tracker, relative to the last synchronization sent to the star tracker.
The star tracker is comparing the image in its focal plane to know configurations of stars, but has not yet recognized the image.
The star tracker is reporting the angular rate vector. This condition implies that the star tracker is tracking or acquiring.
The star tracker has recognized the configuration of stars in its image, and is reporting its attitude.
Variables with this interpretation represent a status, such as an error condition, of a device.
The ternary status convention adds a warning state to the binary status. The three states follow: • OK – no error detected • Warning – action (such as restart) is not needed • Severe – action (such as restart) is needed Use Cases: Distinguish minor errors from major errors.
The transducer reference frame is a special variation on the device reference frame. Some instruments contain multiple transducers. For example, a three-axis magnetometer may consist of three one-axis magnetometers. Usually, the one-axis transducers are arranged parallel to the coordinate axes of the device frame, so no transformation is needed to transform from measurement frame to mount frame. However, some devices may have multiple transducers that are not so fortuitously positioned. In that case, it is necessary to be able to refer to the reference frame of the transducers of a device. Use Cases: Specify the frame of a coarse sun sensor in a device that contains multiple coarse sun sensors arranged to face in non-orthogonal directions. Specify the frame of each of the optical axes of a star tracker with multiple sights
Variables with this interpretation represent a change of coordinate systems.
The “translation” value of the “transformation type” term specifies the following information for a semantic type: • coordinate system = Cartesian • array size = n • unit of measure = length • the transformation is computed by adding this vector to the vector in the reference frame The elements of the vector are interpreted as changes in Cartesian coordinates. The vector is not a position, but is a translation transformation that can be applied to position vectors by adding the translation coordinates to the position coordinates. Chirality of the coordinate system must be specified in an electronic data sheet when using this term. The unit of measure must also be specified in an electronic data sheet when using this term.
This interpretation can be assigned to a time duration argument in a command, in order to define the period of time allowed for execution of the command. Better never than late.
The vehicle reference frame is the base from which a spacecraft conducts its mission. Relations between sensors and actuators are computed through the vehicle frame. Use Cases: Control the direction in which an articulated antenna is pointing relative to the attitude of the vehicle.
This kind of reference identifies a vehicle in a fleet of vehicles. For example, a GPS receiver carries a table of the satellites in the global positioning system with the orbital parameters for each satellite. An index into that table is a vehicle reference number.
The “velocity” value of the “transformation type” term specifies the following information for a semantic type: • coordinate system = Cartesian • array size = n • unit of measure = length / time • the transformation is generally not computed, because this vector is often used directly as a measurement and as a set point for a navigation system The vector represents the rate of translation of the “to frame” relative to the “reference frame”. The elements of the vector are the linear speeds along each axis of the reference frame. Chirality of the coordinate system must be specified in an electronic data sheet when using this term. Unit of measure for the speed must also be specified in an electronic data sheet when using this term.