6
$\begingroup$

As an Electrical Engineer (emphasis in RF and radar, class of '74) who has followed the space program(s) since Mercury, and a prior flight test telemetry engineer, I was wondering if anyone knows what frequency (frequencies), effective radiated power (ERP), and the modulation modes (I am assuming it's PCM) are being used to transmit the SpaceX images from the Tesla in space Roadster? Are they using the TDRSS satellites for data relay (although the data is only high definition images, no usable telemetry metrics that I know of).

I have been watching for any signs of data loss (dropouts) and so far this is still a very strong signal from the "spacecraft". I saw no drop outs as it performed its barbecue continuous yaw thermal control maneuver about its axis; I looked all over the SpaceX website, but there is very little technical information. It would appear that the only antennae are omnidirectional - no sign of a parabolic dish, or X-Y drives for positioning it.

Improve this question
$\endgroup$
2
  • $\begingroup$ Could just be buffered, there's no way to be sure that it's absolutely live that I know of. $\endgroup$
    – uhoh
    Feb 16, 2018 at 14:27
  • 1
    $\begingroup$ I would have to concur - are you aware of any place where raw data would be available? Although this is simply a mass, with Sir Isaac Newton in the suit, its not without scientific merit. - as I said, I have found very little usable engineering data from Space-X in the public domain. -I trust they will be more open in forthcoming missions. $\endgroup$
    – Cynthia_K
    Feb 16, 2018 at 15:44

2 Answers 2

Reset to default
5
$\begingroup$

You can see the FCC launch permit here: https://apps.fcc.gov/oetcf/els/reports/STA_Print.cfm?mode=current&application_seq=80036

(STA is a Special Temporary Authority) "Application includes three sub-orbital first stage boosters, and an orbital second stage."

There are separate listings for "Launch vehicle 1st stage, sub-orbital", "Launch vehicle 2nd stage, orbital", "Launch vehicle S1-a, sub-orbital ", and "Launch vehicle S1-b, sub-orbital". Together, they have six 20W emitters with frequencies from 2211 to 2375 MHz and bit rates from 2.777 Mbps to 6.25Mbps.

Interestingly, they left the answer to "height above ground to tip of antenna" blank.

Improve this answer
$\endgroup$
1
  • $\begingroup$ oh, that is a nice find, the documents also list the emmision designator Some are FM, some are PM... very good. $\endgroup$
    – Edwin van Mierlo
    Feb 19, 2018 at 8:21
4
$\begingroup$

That is a lot of questions, let me try to address them one by one:

I was wondering if anyone knows what frequency (frequencies), effective radiated power (ERP), and the modulation modes (I am assuming it's PCM) are being used

There has been little in the public domain in regards to the on-board RF equipment of the Falcon-Heavy, and it is assumed no RF equipment on the Tesla (e.g. it is using 2nd stage infrastructure).

From a related question & answer the frequencies of the Falcon-9 are well documented, including their Pout in dBm, purpose, and modulation, the following from newer (Rev-2) version of the Falcon-9 user-guide:

enter image description here

Whether they actually used PCM modulation is not certain. The older Falcon-9 (Rev-1) user-guide actually lists NTSC as a feed protocol for Stage-2 Video, Page 37, Table 5.2:

enter image description here

The newer (Rev-2) version of the Falcon-9 user-guide does not list this type of table, nor does in mentions NTSC at all.

Are they using the TDRSS satellites for data relay (although the data is only high definition images, no usable telemetry metrics that I know of)

They are not, the just over 4-hour live feed came from the Stage-2 directly, until batteries ran out (8-hours sooner than expected)

I have been watching for any signs of data loss (dropouts) and so far this is still a very strong signal from the "spacecraft". I saw no drop outs as it performed its barbecue continuous yaw thermal control maneuver about its axis; I looked all over the SpaceX website, but there is very little technical information.

Unfortunately the live-feed has ceased due to battery depleation. The only video's left on the internet are re-runs of the first 4 hours. Although you can find lots of references that the video ran out after 4 hours, none of them are authoratitive. Most of them are news outlets, with various levels of trustworthyness.

However SpaceX own website has an article which clearly details the following:

"You can watch a replay of the test flight below, as well as a replay of the live view of Starman in orbit"

One may safely assume there is no longer a live feed, when the best SpaceX themselves have; is a replay.

It would appear that the only antennae are omnidirectional - no sign of a parabolic dish, or X-Y drives for positioning it.

It is not sure what type of antennas, omnidirectional or directional, are on the Falcon-Heavy. Again referencing an older Rev-1 Falcon-9 user-guide Page 11, does show us the design for that launch vehicle:

enter image description here

Again, it is logical to assume that the Falcon-Heavy is similar than the Falcon-9 in this regard.

Without actual details in the public domain on the Falcon-Heavy, this answer is unfortunately based on quite some assumptions. Nevertheless, it will give you a good idea how communications could have been handled.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.