By accident I have just

Forums Asteroids New Horizons about to fly past ‘Ultima Thule’ By accident I have just

Nick James

By accident I have just deleted my original comment. so I’ve reconstructed it below. It is a bit techy but basically the data rate back from NH is around 1kbps (equivalent to around 5hrs to transmit a mobile phone picture) achieved using a transmitter with the power of a small LED lightbulb.

The data rate from NH is around 1kbps at the moment achieved using a 12W transmitter and a 2.1m high gain antenna on board the spacecraft. This is received by a 70m DSN antenna on the ground. The link is at X-band and the data is encoded using a rate 1/6 Turbo code. This expands every bit of data into 6 symbols which are then transmitted to the ground. The coding allows the ground to extract good data at a very low signal-to-noise ratio (Eb/No = 0dB). The data is partially phase modulated onto a carrier with some power remaining in the carrier. This provides a discrete frequency tone for synchronisation.

For those that are interested the link budget goes something like:

Spacecraft downlink EIRP +52.8dBW
Free space path loss -307.2 dB
DSN antenna G/T +61.5dB/K
Boltzmann constant +228.6 dBW/K/Hz
Bit rate -30dBHz
Eb/No 5.7 dB

The actual margin is much less than this since NH is currently very near solar conjunction (6 deg today, down to 2 deg on Jan 7) and I haven’t included any factors for transmit and receive losses, modulation loss, pointing losses, weather etc.

A fun fact is that NH is currently around 6.6 billion Km away which is around 160000 times further than a geostationary satellite so the path loss is around 104dB larger than from GEO. That’s a lot.