ExampleSat

This repository contains an example of how we can implement an interface using TelemetryAnalysis.jl with a hypothetical satellite called ExampleSat.

Telemetry Format

The telemetries of our hypothetical satellite are available in a text file where each line has the following format:

<ID> <telemetry><crc>

The <ID> is an incrementing counter with 5 digits, and <telemetry> is a set of 29 bytes with the telemetry frame. Those 29 bytes contains the information about the following variables:

Name	Alias	Description	Start byte	Size [bytes]
V001	obt	Onboard time (number of seconds from GPS epoch)	1	4
V002	mode	Satellite operating mode	5	1
V003	vR_tod_x	Satellite X-axis position represented in the TOD reference frame	6	4
V004	vR_tod_y	Satellite Y-axis position represented in the TOD reference frame	10	4
V005	vR_tod_z	Satellite Z-axis position represented in the TOD reference frame	14	4
V006	vR_tod_x	Satellite X-axis velocity represented in the TOD reference frame	18	4
V007	vR_tod_y	Satellite Y-axis velocity represented in the TOD reference frame	22	4
V008	vR_tod_z	Satellite Z-axis velocity represented in the TOD reference frame	26	4
V009	passage_type	Ascending or descending passage	-	-

Notice that V009 is what we call a derived variable. It depends on the values of other telemetries but does not have a direct relationship to a set of bytes in the frame.

All variables are stored in big endian format (most significant byte first).

The <crc> is the sum of all bytes converted to a UInt16.

Telemetry Transfer Functions

We also need to define how we can convert the sequence of bytes in each variable to a processed value.

• obt: Number of seconds elapsed from GPS epoch.
• mode: Direct conversion using the table below.
• vR_tod_{x, y, z}: A set of 4 bytes describing a Float32.
• vV_tod_{x, y, z}: A set of 4 bytes describing a Float32.
• passage_type: Ascending if vV_tod_z >= 0, or descending otherwise.

Interface

The package ExampleSatTelemetry.jl implements the source interface and database, as required by TelemetryAnalysis.jl. For more information about the implementation, refer to the files ./src/source.jl and ./src/database.jl.

Usage

First, we need to load the packages:

julia> using TelemetryAnalysis, ExampleSatTelemetry

Now, we can initialize the telemetry source using the example file with the telemetries:

julia> init_telemetry_source(ExampleSatTelemetrySource, "examples/ExampleSatTelemetry.txt")

Let’s load all the available telemetries:

julia> tms = get_telemetry()
30000-element Vector{TelemetryPacket{ExampleSatTelemetrySource}}:
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T11:00:01, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T11:00:02, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T11:00:03, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T11:00:04, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T11:00:05, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T11:00:06, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T11:00:07, 31 bytes)
 ⋮
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T19:19:54, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T19:19:55, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T19:19:56, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T19:19:57, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T19:19:58, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T19:19:59, 31 bytes)
 TelemetryPacket {ExampleSatTelemetrySource} (Timestamp = 2021-06-19T19:20:00, 31 bytes)

Finally, we can process all the variables:

julia> df = process_telemetry_packets(
           tms,
           [:V001, :V002, :V003, :V004, :V005, :V006, :V007, :V008, :V009]
       )
Progress: 100%|██████████████████████████████████████████████████| Time: 0:00:00
[ Info: 30000 packets out of 30000 were processed correctly.
30000×10 DataFrame
   Row │ timestamp            V001                 V002      V003        V004        V0 ⋯
       │ DateTime             DateTime             String    Float32     Float32     Fl ⋯
───────┼─────────────────────────────────────────────────────────────────────────────────
     1 │ 2021-06-19T11:00:01  2021-06-19T11:00:19  Stand-By   0.0         0.0        0. ⋯
     2 │ 2021-06-19T11:00:02  2021-06-19T11:00:20  Stand-By   0.0         0.0        0.
     3 │ 2021-06-19T11:00:03  2021-06-19T11:00:21  Stand-By   0.0         0.0        0.
     4 │ 2021-06-19T11:00:04  2021-06-19T11:00:22  Stand-By   0.0         0.0        0.
     5 │ 2021-06-19T11:00:05  2021-06-19T11:00:23  Stand-By   0.0         0.0        0. ⋯
   ⋮   │          ⋮                    ⋮              ⋮          ⋮           ⋮          ⋱
 29996 │ 2021-06-19T19:19:56  2021-06-19T19:20:14  Mission   -2.65117e6  -3.97796e6  5.
 29997 │ 2021-06-19T19:19:57  2021-06-19T19:20:15  Mission   -2.64952e6  -3.97254e6  5.
 29998 │ 2021-06-19T19:19:58  2021-06-19T19:20:16  Mission   -2.64786e6  -3.96712e6  5.
 29999 │ 2021-06-19T19:19:59  2021-06-19T19:20:17  Mission   -2.64621e6  -3.96169e6  5. ⋯
 30000 │ 2021-06-19T19:20:00  2021-06-19T19:20:18  Mission   -2.64455e6  -3.95625e6  5.
                                                         5 columns and 29990 rows omitted