The DSN operates primarily on two bands, S-band and X-band. We are beginning to support some missions with a higher frequency, Ka-Band.

The frequencies are separate for Transmit (Earth to Space) and Receive (Space to Earth):

Yes, we actually have transmitters that range from about 16 watts to 400 kilowatts and like you said, the choice of the transmitter depends on basically how far the spacecraft is away; and also it can depend on the attitude of the spacecraft. If for some reason, the spacecraft is in an unfavorable attitude, we tend to go to higher transmitter powers, to be able to assure that we can get commands into it. The spacecraft usually transmit ~ 20 watts.

The small transmitters on board the spacecraft transmit very weak signals, made weaker by the great distances they must travel. One of the challenges for the DSN is to receive this data. There are several approaches to improving the received telemetry - using higher microwave radio frequencies, telemetry coding techniques, state-of-the-art sensitivity of the system, and low-noise receivers. Low-noise receivers comprise a preamplifier and an amplifier mounted on the antenna, and a receiver located away from the antenna in the signal processing center. A key to overcoming noise sources is the "maser" (Microwave Amplification by Stimulated Emission of Radiation) in the preamplifier. The core of the maser is synthetic ruby crystal, placed in a strong magnetic field, and cooled with liquid helium to near absolute zero.

We use error correcting codes developed by our engineers here at JPL. One method used is to use a code which includes known additional information in the encoded data to aid in detecting and correcting errors. With sufficient redundant digits, if single or multiple errors occur, the original data can be reconstructed.

Unfortunately, no. Spacecraft signals are very weak by the time they reach Earth which is why we need the huge reflector dishes of the Deep Space Network antennas as well as the sophisticated amplifiers and other signal enhancing electronics to hear them. Amateur radio equipment and antennas cannot receive such weak signals.

Images, as well as other instrument data, is transmitted by a low power transmitter on board the spacecraft using microwave radio frequencies. The data is converted by an on board computer to binary code (0's and 1's) and sent as a digital 'bitstream'. (See the Bringing Images from Space to Earth Tutorial.)

The transmission time for a picture consists of two major components.

1. The amount of time required to send the data (i.e. transmit) from the spacecraft antenna toward Earth.
2. The amount of time that it takes the signal to travel from the spacecraft to the Earth.

On the Mars Pathfinder mission, the first time varied depending on the transmission data rate (e.g. 10K bits per second), the size of the image (e.g. 1.2 megabits), and the compression level applied to the image (e.g. 12 to 1 compression). Thus this time on Pathfinder varied between a few seconds to several minutes.

The second time is simply the range (distance) between the Earth and Mars divided by the speed of light (186,000 miles per second). This time for Pathfinder started at about 10 minutes and increased several minutes by the end of mission.

Spacecraft exploring at a greater distance than Mars, require longer times. Voyager I is out beyond our furthest planet. When it was 7,555,000,000 miles from Earth, the round trip time for a signal to be sent and acknowledged in return was 22 hours 18 minutes. It moves further away as each day passes, traveling at over 91,000 miles per hour.

Typically, if we have more than one spacecraft that's in the same beam width of the antenna, like we have had with Mars Global Surveyor and Mars Odyssey, we'll be able to track both simultaneously even though they are using different frequencies. Part of our preparation for a mission is to practice that. So we'll actually be receiving downlinks from two spacecraft, gathering all the telemetry and sending it offsite; and then we'll uplink to only a single spacecraft or command only a single spacecraft at a time.

Oh, yes, absolutely. One example is Voyager II. It was doing a radio science experiment that was planned to happen over the large antenna in Madrid. The rain in Spain that day was definitely not on the plain! And actually washed out the event.

If the weather completely attenuates the signal, then it's lost. But we've tried to pick places for the complexes that have less than normal types of rainfalls, and the projects try to choose their trajectories so that events occur during periods of the year where we aren't subject to those types of things, but it does happen.

We have a system that exists just at Goldstone, which is a very high-powered transmitter that's deliberately not the same frequency as we send to spacecraft. We use it to do radar observations. The reason we have it is to do scientific observations, where we send a signal and bounce it off an asteroid or a planet and receive it. From science team processing, they can construct things equivalent to images or texture diagrams. That very same system is used from time to time to locate orbital debris for the manned program. Yes, we have done that.