position.md

Azure Orbital Space SDK - Position Service (hostsvc-position)

The Position Host Service provides current position and orientation data for satellite payloads. This service allows payload applications to track the satellite's orbit to support mission planning, navigation, and payload targeting.

Key Features

• Real-Time Data Access: Provides access to the latest position and orientation data of the satellite, ensuring that payload applications have the most current information.

• Local Cache System: Utilizes a local cache to store the last known position and orientation, allowing for quick retrieval and eliminating the need to poll satellite subsystems for updates.

• Asynchronous Updates: Receives updates asynchronously through PositionUpdateRequest messages, ensuring the data remains current.

• SDK Integration: Offers easy integration with payload applications through an SDK client library, simplifying the process of requesting and receiving position data.

Use Cases

• Mission Planning: Enables precise planning of satellite operations by providing accurate position and orientation data, crucial for aligning payloads and calculating orbital trajectories.

• Payload Targeting: Allows payload applications to accurately target their operations, whether for communication, observation, or scientific experiments, based on the satellite's current location and orientation.

Position Host Service Operations and Workflows

Receiving Position Data

The position host service can be used by payload applications to get the last known location and orientation of the spacecraft. This process begins by the payload application sending a PositionRequest message to the position host service through an SDK client library. Upon receiving this message the position host service retrieves the last known location and orientation of the spacecraft from its internal cache, which it returns to the payload application in the form of a PositionResponse message.

Updating Position Data

The position host service's local cache of the last known location and orientation of the spacecraft is updated asynchronously from PositionRequest messages via PositionUpdateRequest messages sent by the Message Translation Service (MTS). The Message Translation Service interfaces with the satellite's various subsystems, including those governing guidance and navigation. As theses subsystems broadcast position and orientation updates the MTS forwards them to the SDK runtime framework by publishing a corresponding PositionUpdateRequest message to the position host service. Upon receiving this message and updating its local cache the position host service responds to MTS with a PositionUpdateResponse verifying receipt of the request.

Position Data Sequence Diagram

sequenceDiagram
    participant PA as Payload Application
    participant PS as Position Host Service
    participant MTS as Message Translation Service
    participant SS as Satellite Subsystems

    PA->>PS: PositionRequest
    PS->>PS: Read Local Cache
    PS->>PA: PositionResponse

    SS->>MTS: Broadcast Position and Orientation Updates
    MTS->>PS: PositionUpdateRequest
    PS->>PS: Update Local Cache
    PS->>MTS: PositionUpdateResponse

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Position Host Service Use Examples

The following C# example demonstrates how to request the last known position of the satellite using the Azure Orbital Space SDK .NET Client Library:

using System.Threading.Tasks;

using Microsoft.Azure.SpaceFx;
using Microsoft.Azure.SpaceFx.MessageFormats.HostServices.Position;

Client.Build();

Task<PositionRequest> positionRequestTask = Microsoft.Azure.SpaceFx.SDK.Position.LastKnownPosition();
positionRequestTask.Wait();

PositionResponse positionResponse = positionRequestTask.Result;

The following Python example demonstrates how to request the last known position of the satellite using the Azure Orbital Space SDK Python Client Library:

import spacefx

spacefx.client.build()

position_response = spacefx.position.request_position()