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Space Media Technology

SpaceX Looking For Help With "Landing" Video 110

Posted by samzenpus
from the clean-it-up dept.
Maddog Batty (112434) writes "SpaceX recently made the news by managing to soft land at sea the first stage of rocket used to launch its third supply mission to the International Space Station. Telemetry reported that it was able to hover for eight seconds above the sea before running out of fuel and falling horizontal. Unfortunately, due to stormy weather at the time, their support ship wasn't able to get to the "landing" spot at the time and the first stage wasn't recovered and is likely now on the sea bed. Video of the landing was produced and transmitted to an aeroplane but unfortunately it is rather corrupted. SpaceX have attempted to improve it but it isn't much better. They are now looking for help to improve it further."
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SpaceX Looking For Help With "Landing" Video

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  • Neat (Score:5, Insightful)

    by durrr (1316311) on Wednesday April 30, 2014 @06:05PM (#46885097)

    I appreciate them looking for public help. It's a gesture of trust and openness usually not seen from either goverment or private corporations.
    Though I suspect most the the video is beyond salvage.

  • Re:Missing video (Score:5, Insightful)

    by Guspaz (556486) on Wednesday April 30, 2014 @07:36PM (#46885693)

    Errm, they did have a well planned means to evaluate success: telemetry data. Which they have good copies of. The video is just candy.

  • by Required Snark (1702878) on Wednesday April 30, 2014 @10:03PM (#46886333)
    I think you are living in the past. To the best of my knowledge nobody records analog data streams for digital video. There is very little analog hardware in the system. The analog signal pretty much goes through an A/D converter as soon as possible, and the error correction is digital.

    Terrestrial broadcast HDTV in the US uses 8VSB [wikipedia.org] encoding:

    8VSB is an 8-level vestigial sideband modulation. In essence, it converts a binary stream into an octal representation by amplitude modulating a sinusoidal carrier to one of eight levels. 8VSB is capable of transmitting three bits (2^3=8) per symbol; in ATSC, each symbol includes two bits from the MPEG transport stream which are trellis modulated to produce a three-bit figure. The resulting signal is then band-pass filtered with a Nyquist filter to remove redundancies in the side lobes, and then shifted up to the broadcast frequency.

    Somehow I doubt that "analog filters can be applied to that in an attempt to create a cleaner input signal to the demodulator stage". That part of the system is already highly optimal.

    Additionally, it's not telemetry [wikipedia.org] data in the first place.

    A telemeter is a device used to remotely measure any quantity. It consists of a sensor, a transmission path, and a display, recording, or control device. Telemeters are the physical devices used in telemetry. Electronic devices are widely used in telemetry and can be wireless or hard-wired, analog or digital.

    It's not from the rocket stage, it's from an aircraft observing the splashdown. This is more remote sensing. I know that this is a quibble, but you seem to be confused about the nature of data sources and encoding.

  • by larwe (858929) on Wednesday April 30, 2014 @10:32PM (#46886479) Homepage
    There is so much wrong in this I barely know where to begin. Nobody records analog streams for digital TV data, but this is completely irrelevant. Everybody records analog streams for spacecraft telemetry because you can't post-analyze an improperly demodulated digital data recording. Doppler velocity measurement is also performed from the raw signal, for example by mixing with a signal at the original (TXCO-controlled) carrier frequency and observing the beat. The A/D stage is NOT demodulation, it's digitization. A digitized recording of an analog waveform is nothing even remotely akin to recording the binary output of a demodulator stage. (For practical purposes, a modern recording would, indeed, be digital - but it would be a digital recording of the original received waveform, not simply a recording of the realtime output from a demod). Having the original waveform to look at allows different types of filters to be tried and applied, not just the single set of parameters that were in the realtime decoder on board the aircraft. It's absolutely the baseline for data recovery in this type of application. Telemetry = "remote measurement", a term used to refer to data streams downlinked from the vehicle that are not crew communications or control data, which includes still and moving image data.

If the code and the comments disagree, then both are probably wrong. -- Norm Schryer

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