# How many communications channels can a single DSN dish maintain at the same time?

DSN NOW screenshot 2021-07-10 at 07:14 UTC

DSN NOW screenshot 2021-07-10 at 09:48 UTC

The screen shots show Canberra's Dish 35 simultaneously transmitting and receiving, and above it is written MRO, MSL and TGO which represent Mars Reconnaissance Orbited, Mars Science Laboratory (Curiosity) and the Trace Gas Orbiter, and MADRID's Dish 55 likewise with M01O, M20, MEX and MRO above it which are Mars Odyssey, Mars 2020 (Perseverance), Mars Express and Mars Reconnaissance Orbiter.

Note that Curiosity and Perseverance can communicate with Earth through an orbiter and also directly; for more on that see:

I clicked on the dish and inspected and copied all of the displayed data and have pasted it below.

This is just an example as background to explain the origin of the question.

Question: How many communications channels can a single DSN dish maintain at the same time? Don't count store-and-forward scenarios as multiple spacecraft, e.g. if MRO assists in communication between Curiosity and DSN then only count MRO. But if there are both up and down channels (transmit and receive) for a given spacecraft at the same time that would count as two channels.

ANTENNA NAME:       DSS 35
AZIMUTH:      312.78 deg
ELEVATION:     22.88 deg
WIND SPEED:     4.94 km/hr
MODE:           MSPA

UP SIGNAL:             MARS RECONNAISSANCE ORBITER
TYPE:                 DATA
DATA RATE:
FREQUENCY:            7.18 GHz
POWER TRANSMITTED:    4.96 kW

DOWN SIGNAL SOURCE:    MARS RECONNAISSANCE ORBITER
TYPE:                 DATA
DATA RATE:          999.97 kb/sec
FREQUENCY:            8.44 GHz
POWER RECEIVED:    -122.10 dBm   (6.17 x 10-19 kW)

DOWN SIGNAL SOURCE:    TRACE GAS ORBITER
TYPE:                 DATA
DATA RATE:          312.49 kb/sec
FREQUENCY:            8.41 GHz
POWER RECEIVED:    -126.94 dBm  (2.02 x 10-19 kW)


ANTENNA NAME:       DSS 55
AZIMUTH:      90.18 deg
ELEVATION:     26.31 deg
WIND SPEED:     7.41 km/hr
MODE:           MSPA

UP SIGNAL SOURCE:      MARS 2020 (PERSEVERANCE)
TYPE:                 DATA
DATA RATE:
FREQUENCY:            7.16 GHz
POWER TRANSMITTED:   17.55 kW

DOWN SIGNAL SOURCE:    MARS ODYSSEY
TYPE:                 DATA
DATA RATE:           14.22 kb/sec
FREQUENCY:            8.41 GHz
POWER RECEIVED:    -135.92 dBm   (2.56 x 10-20 kW)

DOWN SIGNAL SOURCE:    MARS EXPRESS
TYPE:                 DATA
DATA RATE:           65.53 kb/sec
FREQUENCY:            8.42 GHz
POWER RECEIVED:    -126.89 dBm  (2.05 x 10-19 kW)

• It depends on the bandwidth of the receiver and the bandwidth of the channels. If you have 100 MHz bandwidth on the receiver, you could fit ten 10 MHz channels in there, or five 20 MHz, or a hundred 1 MHz channels.
– Ludo
Jul 11 at 19:49
• @Ludo I'm asking about the actual hardware capability of a DSN dish and it's associated infrastructure and the nature of spacecraft at Mars, not about communications theory 101. There are potentially issues of scheduling, billing, dish beam width, data preparation and confirmation, encoding, stop bands between signals for safety, spacecraft bandwidths (you don't want two signals to fall within a given spacecraft's bandwidth for reasons of safety) and that's just off the top of my head. This is no a simple question to answer.
– uhoh
Jul 12 at 0:54
• I mean that an answer is meaningless without considering also the spacecraft-end of the channel and the signal processing after receiving. The "dish" can support infinitely many, just not in a meaningful way. Maybe it's better to ask what is the highest number of spacecraft a single dish has communicated with simultaneously.
– Ludo
Jul 12 at 13:22
• @Ludo By "DSN dish" I mean the whole DSN infrastructure, data management chain and hardware, not just the parabolic conducting primary surface. I'd thought about asking for "the highest number" but then the answer might simply be a single sentence with a number and a link and then we learn nothing from it. Written as a question about capability, the answer will have to go into some detail and therefore be a much more valuable answer for future readers of the site.
– uhoh
Jul 12 at 13:36
• @Ludo there are also answers here about frequency spacing of existing spacecraft, so there is some information on this available as well. Let's see where this goes, there might just be a DESCANSO article out there that sheds some light on this.
– uhoh
Jul 12 at 13:38