Mars scientists wish they had dial-up speed (Some detail on the communications from Mars)

The Orange County Register ^ | Saturday, January 31, 2004 | GARY ROBBINS and TAMARA CHUANG

[Ernest_at_the_Beach]

SLO-MO: The Mars rovers Spirit and Opportunity have been transmitting captivating images of the Red Planet to Earth

[Ernest_at_the_Beach]

Now this is an article that is very useful!

[Ernest_at_the_Beach]

fyi

[Ernest_at_the_Beach]

What is the speed of the High Gain antenna that can communicate directly with earth?

[GeronL]

wait a sec... I thought they were able to get communications speeds of 182 kpbs.... in another article...

I guess someone messed up in the other article..

[dr_who_2]

It's nice to know that they'll have trouble uploading MP3's of Nora Jones tunes to Mars. Slim Whitman would be bad enough. Or Sarah McGlaegchlan. "I will disMEMber you. Will you disMEMber me?"

[LibWhacker]

I interpreted it to mean 11,000 bits per second using the high gain antenna. But I'm wondering about something else . . . 11,000 bps is 1,375 bytes per second, a LOT slower than one-fifth the speed of a 56k modem.

[DB]

I think that is the speed of the high gain antenna.

When using the regular antenna the speed is much slower.

[LibWhacker]

Hmmm . . . What are kpbs? I've heard of kilobits per second and kilobytes per second, but can't find anything about kpbs.

[jennyp]

I interpreted it to mean 11,000 bits per second using the high gain antenna. But I'm wondering about something else . . . 11,000 bps is 1,375 bytes per second, a LOT slower than one-fifth the speed of a 56k modem.

No, 56 kbps is 56,000 bits per second, or 5,600 bytes per second. (10 bits per byte due to the start & stop bits.) Also, assuming they're using a somewhat standard protocol on that level, 11,000 bps would be 1,100 bytes per second.

[LibWhacker]

Oh, okay . . . I thought a 56k modem meant 56 kilobytes per second. Man, it's hard to keep this stuff straight!

[GeronL]

KPBS is probably a public television station or something..

[LibWhacker]

It must mean kilopixels per second. If each pixel has 64 bits of info in it (color and brightness level, say), that would be about right for a 11,000 bps high gain antenna.

[NormsRevenge]

Bump.. I remember seeing the comm specs on one of the jpl/rover sites. I'll see if can dig it up.

[LibWhacker]

LOL

[Ernest_at_the_Beach]

Man, it's hard to keep this stuff straight!

I worked around computers for years and never kept it straight!

I was not a specialist on Ack's and Nak's!

[Professional Engineer]

By comparison, Norah Jones' MP3 song "Cold, Cold Heart" is 5.4 megabytes. And it lasts only 4 minutes and 40 seconds.

Good thing they're only comparing. the RIAA would be after NASA otherwise.

You're right, this is useful information.

[Ernest_at_the_Beach]

Good, I was looking but didn't find it!

[Amerigomag]

11,000 bps is 1,375 bytes per second, a LOT slower than one-fifth the speed of a 56k modem

11,000 bits per second = 1375 bytes per second = 1.375 kilobytes per second.

56K = 56,000 bits per second = 7000 bytes per second = 7 kilobytes per second.

Typical analog modems rated at 56K run max speeds of 49K to 52K by both circumstance and design. 38K to 40K is not unusual in older telco environments.

Therefore 11,000 bits per second can be more than 40% of common analog modem speeds and is slightly more than 20% of the speed of an analog modem operating at it's design capacity .

Hope this helps.

[spunkets]

128k is pretty good for an RF modem. THey can do that between the rover and Odessey, because they can use a high enough frequency. For transmission to Earth they need to encrypt the data, so no one knows they're really comms with the Martian equivalent of Earth's UN.

Just kidding... The to Earth data rate is limited, because they have to use a lower frequency to balance transmittion power and loss considerations. The power sourses on those ships are limited. If they had better microwave aiming, they could use lower power focused beams to an Earth satellite and relay to Earth on another frequency. That's still ~56k down depending on power available.

[Saturnalia]

That's what they get for trying to download dirty pictures at the dame time!