spaceToGroundTransmitter#

Executive Summary#

This module provides a model of access-dependent data downlink from a simple transmitter at a fixed baud rate. Specifically, the transmitter reads a DataStorageStatusMsgPayload from the storage unit it is subscribed to, searches for the data buffer with the maximum amount of data, and downlinks a packet of data at a fixed baud rate. The transmitter writes out a DataNodeUsageMsgPayload describing the data name and baud rate of the data it wants to downlink.

In comparison to simpleTransmitter, downlink is only enabled when a AccessMsgPayload indicates that the spacecraft for which the transmitter is associated has access to an object that can provide it (such as a groundLocation.)

For more information on how to set up and use this module, see the simple data system example: scenarioDataDemo

Module Assumptions and Limitations#

This module makes no additional assumptions outside of those already made in the DataNodeBase base class.

Message Connection Descriptions#

This module uses the input and output messages of the DataNodeBase base class, plus an additional DataStorageStatusMsgPayload input message subscribed to and read customRead() method.

Module I/O Messages#
Msg Variable Name	Msg Type	Description
storageUnitInMsgs	DataStorageStatusMsgPayload	Vector of storage units that are connected to the transmitter. Add storage unit with the `addStorageUnitToTransmitter` method.
groundAccessInMsgs	AccessMsgPayload	Vector of access messages available to the transmitter. Add input messages with the `addAccessMsgToTransmitter` method.

User Guide#

This module inherits the user guide from the DataNodeBase base class, but there are several key differences from other DataNodeBase child classes:

Unlike other child classes of DataNodeBase, this module does not require a user to set a nodeDataName
The nodeBaudRate variable should be set to a negative value in order to remove data from the storage unit.
The user must specify a packetSize variable (negative value) in addition to the nodeBaudRate variable
The user must specify the number of buffers numBuffers variable so the transmitter knows how many buffers to search through
The user must specify the storage unit the transmitter should subscribe to using the addStorageUnitToTransmitter()` method

To set up this module users must create a SimpleTransmitter instance:

transmitter = spaceToGroundTransmitter.SpaceToGroundTransmitter()
transmitter.modelTag = "transmitter"

Set the nodeBaudRate, packetSize, and numBuffers variables:

transmitter.nodeBaudRate = -16000. # baud
transmitter.packetSize = -1E6 # bits
transmitter.numBuffers = 2

The next step is to attach one or more DataStorageStatusMsgPayload instances to it using the addStorageUnitToTransmitter() method:

transmitter.addStorageUnitToTransmitter(storageMsg)

Next, attach available AccessMsgPayload instances using the addAccessMsgToTransmitter() method:

transmitter.addAccessMsgToTransmitter(accessMsg)

The final step is to add the model to task:

scenarioSim.AddModelToTask(taskName, transmitter)

Follow the partitionedStorageUnit or simpleStorageUnit instructions to add the transmitter to a storage unit.

For more information on how to set up and use this module, see the simple data system example: scenarioDataDemo

Class SpaceToGroundTransmitter#

class SpaceToGroundTransmitter : public DataNodeBase#

space to ground data transmitter class

Public Functions

SpaceToGroundTransmitter()#: Constructor, which sets the default nodeDataOut to zero.

void addStorageUnitToTransmitter(Message<DataStorageStatusMsgPayload> *tmpStorageUnitMsg)#

Adds a dataStorageStatusMsgPayload name to be accessed by transmitter.

Parameters:: tmpStorageUnitMsg – A spacecraft state message name.
Returns:: void

void addAccessMsgToTransmitter(Message<AccessMsgPayload> *tmpAccessMsg)#

Adds a msg name to ground location access list

Parameters:: tmpAccessMsg – input name.
Returns:: void

Public Members

double packetSize#: Size of packet to downklink (bytes)

int numBuffers#: Number of buffers the transmitter can access.

std::vector<ReadFunctor<DataStorageStatusMsgPayload>> storageUnitInMsgs#: vector of input messages for storage unit messages

std::vector<ReadFunctor<AccessMsgPayload>> groundLocationAccessInMsgs#: vector of input message for ground location access

std::vector<DataStorageStatusMsgPayload> storageUnitMsgsBuffer#: local copy of data storage messages

uint64_t hasAccess#: class variable

BSKLogger bskLogger#: class variable