Follow PicSat on
   Twitter30width    Youtube30width
French version   English version    
Logo transparent
Unravelling the Beta Pictoris System
MISSION STATUS:
Picsat is: not responding since 2018-03-20
Number of telemetry packets received today:
0
Last beacon satellite:
2018-04-07 20:45:22 UTC

Last beacon payload:
2018-03-20 01:00:08 UTC

Uplink is not active
Downlink is not active

Telemetries Overview

What are telemetry packets?

The space segment (also known as "the satellite") of a space mission generates a lot of data, which must be transferred to the ground segment (aka the ground station) via the radio-communication link. These data which go from space to ground (downlink) are called telemetries, and can be of several different sorts, from science data to house-keeping data, or even error reports.

The Picsat mission uses a specific packet communication protocol, based in large part on the CCSDS (Consultative Comittee for Space Data Systems) standards, to transfer telemetries generated in space to the Earth. In this standard, a packet, which represents the elementary piece of information which can be transferred, may contain multiple datapoints, but all of the same type (house-keeping data are never mixed with science data, error reports are not mixed with house-keeping or science data, etc.). During radio communications, a packet is considered to be absolutely indivisble. If only one byte is missing at the receiving end, the packet cannot be decoded, and all the data contained within are lost.

Telemetry packet categories

In the PicSat mission, there are a total of 28 different categories, each dedicated to a specific type of data:

What is the life cycle of a telemetry packet?

Multiple different data are constantly being genereated withing the satellite subsystems (sensors are acquiring measurements, the processor is converting raw science to reduced science, event reports are generated, crucial information about the states of the different subsystems are stored in memory, etc.). These data stored in the memory of the satellite cannot be analyzed by our team of Earthling scientists until they are physically somewhere down here. The only way to get these data on the ground is to sent them from space to Earth using the PicSat onboard radio transmitter. But for them to be properly received by a ground station located at least 600 km below the satellite, they need to be properly sorted and organized. These data are thus aggregated by the processor to form homogenous data packets (or frames). These CCSDS packets typically have a size of about 200 bytes, and can be directly sent to the ground, or stored in the SD card to be retrieved later on.

When a packet is transmitted by the satellite, and retrieved by a station on Earth, it is unpacked, and the data contained within are automatically read by a computer, and stored in a dedicated database located at LESIA, in Meudon, France. This database can then be accessed by our automatic data reduction software to be further processed, and then by our team to be analysed. The database is also directly accessed by this website to generate the graphs and plots you can see here and there.

If you have set up your own station and have already started to receive data from our satellite, you also have access to the unpacked data you received and uploaded on this site. You can use our download page (availble after the launch) to retrieve them on your computer and do whatever you want with them. These data are yours!

Telemetries receieved per day (last 10 days)
Telemetries received per category
Telemetries received per user