Deep Space Network NOW Website - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: December 21, 2015, 07:31:00 pm
content: http://eyes.nasa.gov/dsn/dsn.htmlJust fascinating stuff. This site shows real time data on various dishes that are part of the DSN (located in Spain, USA and Australia).For example, the 70 metre dish at Canberra, Australia is currently recieving data from Voyager 2 with a data rate of 159 bytes/sec. It gives other stats such as frequency and RX power levels. Just blows your mind considering VGR2 is over 16.5 billion kilometers away.

author: dr.diesel
author_rank: Super Contributor
timestamp: December 21, 2015, 07:43:52 pm
content: That is very cool, thanks for sharing.

author: Homer J Simpson
author_rank: Super Contributor
timestamp: December 21, 2015, 08:53:01 pm
content: I Wow. Look at that power level on Voyager 2.-150 dBm

author: Halcyon
author_rank: Unknown
timestamp: December 21, 2015, 09:01:20 pm
content: Quote from: Homer J Simpson on December 21, 2015, 08:53:01 pmI also think it's mind blowing that we can manage a 1.5Mbit/sec downlink from the Mars Reconnaissance Orbiter at -119 dBm.Yet in parts of metropolitan Australia, we can't manage to get decent internet connections.

author: SL4P
author_rank: Super Contributor
timestamp: December 21, 2015, 10:13:58 pm
content: Around 1967/8 - in the era before video games and political correctness and obscenely security... my father arranged a private tour of Tidbinbilla DSIF (near Canberra), and we received a guided tour of 'everything' unheard of nowadays. Yes I was around 11yo !The 70m dish was still a few km away at Honeysuckle Creek, and was relocated later (that would have been a job!)...I don't think they actually had 'guided tours' as such, but I remember there's was only one room we couldn't enter (which we viewed through a glass sliding door, because they had racks of gear in the process of installation for the 1969 moon landing mission.Back then they liked to stimulate young minds.

author: EEVblog
author_rank: Unknown
timestamp: December 22, 2015, 12:05:57 am
content: WOW!Canberra is currently talking to voyager 1 20 billion km away!

author: EEVblog
author_rank: Unknown
timestamp: December 22, 2015, 12:09:41 am
content: Quote from: Homer J Simpson on December 21, 2015, 08:53:01 pmVoyager 1 at -154dBm!

author: Homer J Simpson
author_rank: Super Contributor
timestamp: December 22, 2015, 02:24:52 am
content: A quick copy from Wikipedia for a reference and comparison on just how low of power that is.Your past Nanowatt, Picowatt and femtowatt. Your are in the range of attowatt and zeptowatt. aW and zW power levals.Received power at -154 dBm should be about 0.00000000000000000039810717055 watts0 dBm 1.0 mW = 1,000 µW Bluetooth standard (Class 3) radio, 1 m range?1 dBm 794 µW?3 dBm 501 µW?5 dBm 316 µW?10 dBm 100 µW Maximum received signal power of wireless network (802.11 variants)?20 dBm 10 µW?30 dBm 1.0 µW = 1,000 nW?40 dBm 100 nW?50 dBm 10 nW?60 dBm 1.0 nW = 1,000 pW The Earth receives one nanowatt per square metre from a magnitude +3.5 star?70 dBm 100 pW?73 dBm 50.12 pW "S9" signal strength, a strong signal, on the S-meter of a typical ham or shortwave radio receiver?80 dBm 10 pW?100 dBm 0.1 pW Minimum received signal power of wireless network (802.11 variants)?111 dBm 0.008 pW = 8 fW Thermal noise floor for commercial GPS single channel signal bandwidth (2 MHz)?127.5 dBm 0.178 fW = 178 aW Typical received signal power from a GPS satellite?174 dBm 0.004 aW = 4 zW Thermal noise floor for 1 Hz bandwidth at room temperature (20 °C)?192.5 dBm 0.056 zW = 56 yW Thermal noise floor for 1 Hz bandwidth in outer space (4 kelvins)?? dBm 0 W Zero power is not well-expressed in dBm (value is negative infinity)

author: SL4P
author_rank: Super Contributor
timestamp: December 22, 2015, 05:06:07 am
content: Just for fun, what is the comparative level of a buzzing mosquito - in a room, field, etc....?

author: SeanB
author_rank: Super Contributor
timestamp: December 22, 2015, 11:08:26 am
content: More impressive is the low transmit power as well from the probe.

author: dr.diesel
author_rank: Super Contributor
timestamp: December 22, 2015, 03:21:07 pm
content: KEPL into Madrid right now, a staggering -174.72 dBm (3.38 x 10-24 kW)!

author: Mechanical Menace
author_rank: Super Contributor
timestamp: December 22, 2015, 05:16:27 pm
content: Very cool but isn't calling it theDeepSpace Network severely prematurely patting ourselves on the back? Wouldn't something along the lines ofThe Just Dipping Our Toes in the Local Pool in Regards toSpace Network be more accurate? It'd also make it more clear that as far as we've gone we're still in our backyard.

author: dr.diesel
author_rank: Super Contributor
timestamp: December 22, 2015, 05:28:52 pm
content: Might as well be Deep Space, took Voyager darn near 40 years to get out that far.It's all Einstein's fault. If he'd not made us infinitely heavy at any speeds useful in space we could expand further.

author: SeanB
author_rank: Super Contributor
timestamp: December 22, 2015, 05:30:29 pm
content: Deep Space compared to the highest manned vehicles have gone, ie lunar orbit.

author: Halcyon
author_rank: Unknown
timestamp: December 22, 2015, 07:40:43 pm
content: Quote from: EEVblog on December 22, 2015, 12:09:41 amIt makes me wonder what kind of data Voyager 1 is sending back and how it's doing it; are they using compression and as the satellite gets further and further out, does that compression need to be updated and improved in order to compensate for the low data rate (and I'm assuming increasing error rate)?According to NASA's website:Science data are returned to earth in real time at 160 bps. Real time data capture uses 34 meter Deep Space Network (DSN) resources with the project goal to acquire at least 16 hours per day of real time data per spacecraft. This goal is not always achieved due to the competition for DSN resources with prime mission projects and other extended mission projects.Once a week per spacecraft, 48 seconds of high rate (115.2 kbps) PWS data are recorded onto the Digital Tape Recorder (DTR) for later playback. An additional 48 seconds are recorded each week on Voyager 1. These data are played back to Earth once every 6 months per spacecraft and require 70 meter DSN support for data capture. After transmission of the data (either real time or recorded) to JPL, it is processed and made available in electronic files to the science teams located around the country for their processing and analysis.Obviously yesterday we were seeing that 160 bps data coming through. But if the on-board data recorder is capturing ~5.5 Mbits of data every week, how do they get all that back down to earth?I'm also amazed that the 'tape' they are using to record data is still functioning. Obviously it'd be some fancy pants material but after 40 years, you'd think the magnetic (?) coating would have worn from read/write cycles.

author: EEVblog
author_rank: Unknown
timestamp: December 23, 2015, 08:11:39 am
content: And what kind of data is it from Voyager I wonder?How valuable is it? and do they send an acknowledge so Voyager knows it's been received?Or is data simply lost if we don't receive it?

author: SeanB
author_rank: Super Contributor
timestamp: December 23, 2015, 08:31:58 am
content: Normal mylar tape, lubricated with whale oil. The data is mostly housekeeping data, like temperatures, pressures, voltages and the data from the remaining sensors still operating, like magnetic field strengths and electric field strengths. Data is not acknowledged, if it is not received it is lost. Whatever is recorded on earth is decoded by the team and analysed, and it is not compressed at all, sent as raw binary data with a checksum every frame. That way you have a chance of fixing a single bit error by extrapolation from the adjacent good frames to recover a value, or to know where the error is and ignore that piece.

author: EEVblog
author_rank: Unknown
timestamp: December 23, 2015, 10:08:59 am
content: Are there any photos of the Voyager tape recorders?

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 23, 2015, 11:29:04 am
content: Quote from: EEVblog on December 23, 2015, 10:08:59 amNot sure how valid this is and there is not much to see, but it's all I could find:http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19990065000

author: SeanB
author_rank: Super Contributor
timestamp: December 23, 2015, 11:39:49 am
content: Quote from: EEVblog on December 23, 2015, 10:08:59 amhttp://descanso.jpl.nasa.gov/monograph/series13/DeepCommo_Chapter3--141029.pdfNo pics, but a good description of the control systems, and that the power input is nominally 48W for the transmit stage. Entire spacecraft has under 250W of power to do everything, and the remaining fuel for attitude control is under 20kg or so.Thanks PA0PBZ for the picture of the 8 track digital data recorder.

author: andycsmith
author_rank: Contributor
timestamp: December 24, 2015, 02:05:01 pm
content: There are some NASA webpages that give the status of the Voyageur 1 & 2 spacecraft.There are weekly reports athttp://voyager.jpl.nasa.gov/mission/weekly-reports/although this stops in early 2015, had not checked for a while.Alsohttp://voyager.jpl.nasa.gov/mission/soe-sfos/tracking_schedule.html