Richard Stephenson

After 15 Year of posting about my passion for NASA and specifically the DSN, I'm finding it harder posting as an individual within the new NASA media framework. Its been a pleasure sharing my experiences and hopefully people have enjoyed them. All the best 😀

@Bernard1963 DSS43 will be covering only VGR 1/2 command supports for the next week or so

Contrary to my post the other day it looks like Canberra DSS43 is still down, possibly brought into use just for a one off with Voyager 2. Voyager1 wouldnt be taking up all the 34m's if DSS43 was available 😞

Thanks everyone 😢. I'll keep the account active, some of my posts will still be relevant into the future. I might start posting about my other passions... I just have to find one 😉

@alpha_adhito We aim in between the two, both see a small loss. For Ka uplink/downlink supports we use an aberration table, which physically offsets the uplink pointing, so no lose.

@nascom1 Oh so enough to cover whole planet and beyond. And also one more question if you don't mind, do you "aim" the antenna forward or behind the object that you track due the planet/spacecraft movement and the signal took a couple minutes to arrive or is it negligible?

@ea4gpz @jimlux Each spacecraft has a designated channel. So only one at a time.

@jimlux @nascom1 Does this transmit multiple uplink carriers or does it rely on multiple spacecraft locking to the same carrier?

@alpha_adhito Mars tends to be X-Band so for a 34M BWG antenna the beamwidth is 66mdeg. For our 70m antenna its 32mdeg

@nascom1 Never thought of that. How big the beamwidth is by the way? (X or S band?)

@VU3BIZ I can't say that rain has a nominal attenuation, but light rain like drizzle can drop the symbol SNR by around 2db, heavy rain 10db.

@nascom1 What is the nominal rain attenuation in KaBand frequency?

@VU3BIZ There are 4 bit rates generally used, increasing as the elevation increases and also dropping with elevation to maintain the 2db margin. The highest is 333,333b/s

@nascom1 What is the data rate of the KaBand signal

@ka9q Correct Turbo 1/6. NRZ-L

@nascom1 What's the turbo code rate, 1/6? And what is the modulation phase shift?

Some nasty weather starting to hit the complex. Just made it back to the ops room before the rain started. Luckily only DSS36 SOHO so S-band which is OK but the DSS35 on Juno both X/ka Band will see an impact from the weather. DSS34,43 are on maintenance.

@xjamesmorris @NASAPersevere The round trip light time makes any real time ARQ impractical. Usually it's a repeat of the data on another support if it's science data. Engineering data is generally lost.

@nascom1 @NASAPersevere How do you handle data loss - is there some kind of ARQ protocol?

@dslsynth @NASAPersevere That's bits/sec

@nascom1 @NASAPersevere Is that 176 bytes/second? Phew! . o O ( #turtlenet )

@VinzR87 @realstealthcow @NASAPersevere Nope, it normal operations for all current and previous rovers

@nascom1 @realstealthcow @NASAPersevere Interesting question and answer, so is it typically used for non nominal scenarios, demanding some kind of priority channel in the communication system? How often has it been used in the Perseverance or other rover and lander missions?

@realstealthcow @NASAPersevere The DTE is for real time low level engineering, they don't have to wait for an orbiting spacecraft to be overhead. All science data goes via our relay spacecraft.

@nascom1 @NASAPersevere quick q please, why the occasional change, if presumably the mars orbiter has a faster data rate to earth?

We’re celebrating two milestones for @CanberraDSN! The complex, which operates four radio antennas for our Deep Space Network, recently marked its 60th anniversary. Now, preparations are underway for a fifth dish that will increase the network's capacity. go.nasa.gov/425X0sc

No its not a DSN Now issue. Currently our network is down for mission net maintenance. Every man, women and their dogs are piggy backing on this time to get jobs done around the network that could have a mission impact if done at any other time.

@Tom1973_1 correct, same data on each polarization

@nascom1 Are left and right channel for the same data?

Now fully "awake" after its little nap its back to its normal configuration for the DSN. Identical telemetry transmitted on both Right and Left polarization and combined on earth to provide a 3db (doubling) gain. New Horizon is still the only spacecraft configured this way.

@moddedLimes Separate PAs on the spacecraft.

@nascom1 just separated right before getting to the vehicle's PA (as in it has 2 PAs for this link?)