After traveling 250,000,000 miles, how much is the laser from the Psyche spacecraft attenuated by having to go through Earth's atmosphere?

Question

I'm actually wondering why they didn't receive the laser signal from a satellite and then and then beam the satellite information to Earth.

The brand new laser receiver at Goldstone.

Answer 1

Absorption depends highly on wavelength. For the 1550 nm wavelength used here, NASA calculated the absorption in dB as a function of viewing angle:

Answer 2

The question is based on two false premises that could have been avoided by a quick check in Wikipedia (i.e. prior reserach):

1. The small optical telescope integrated to DSS-13 could be used to receive data from Psyche
2. A satellite exists or could be easily launched to contain the necessary large telescope and superconducting receiver needed to receive data from Psyche

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Wikipedia's Deep Space Optical Communications; Design tells us that the DSOC system aboard Psyche has a 4 watt 1550 nm near infrared laser to send optical signals back to Earth. This is both

• a very well developed high speed communications diode laser wavelength for fiber optic communications where both fiber attenuation and dispersion can be minimized
• in a very transparent spectral window of Earth's atmosphere, even down to sea level (when the weather is good!) update: that link includes light that reachest the ground by scattering as well as direct. For the direct, un-scattered beam only, @Hobbes' answer shows an example of a NASA calculation - for Pueblo Colorado (a better model for Mt. Palomar than San Francisco) it looks like the loss is about 1.5 to 3 dB, meaning about 70 to 50% transmission.

One could argue that if one needed continuous or on-demand optical access, one would definitely like the receiver to be in LEO, not on the ground, and that will probably happen some day.

• All Optical Global Network - how does the space-to-ground link avoid clouds?
• Will future deep space optical communications "ground stations" actually be in space, or on the ground?

Right now the primary target receiver is not the small optical array at Goldstone, but the 5.1 meter diameter Hale telescope on Mt. Palomar where a special superconducting wire detector will convert those faint laser signals directly to electrical signals without first producing photoelectrons like normal photodetectors do. For more on that, see

• Are direct conversion optical receivers being looked at for future deep-space communication?
• How is the maximum data rate of the Psyche mission's Deep Space Optical Communications (DSOC) system expected to scale with distance?
• this answer to Is it possible to extend high speed data transmission with lasers to the distance Earth to Mars?
• Receiver and transmitter in RF/optic satellite communication: distance vs data rate v2

The image in the question does show the mirrors of an experimental receiver integrated into a Deep Space Network dish. They will collect light signals with this and try to do some analysis, but the system is not equipped with the fast and sensitive superconducting receiver system, so at these long distances and weak signals, and because of its much smaller aperture, it will not perform well enough to to the job that the Hale system can do. Nonetheless they will use it to collect signals with the DSN system and try to make some use of them anyway. From NASA’s Optical Comms Demo Transmits Data Over 140 Million Miles:

JPL recently led an experiment to combine Palomar, the experimental radio frequency-optical antenna at the DSN’s Goldstone Deep Space Communications Complex in Barstow, California, and a detector at Table Mountain to receive the same signal in concert. “Arraying” multiple ground stations to mimic one large receiver can help boost the deep space signal. This strategy can also be useful if one ground station is forced offline due to weather conditions; other stations can still receive the signal.

The image in the question is described in NASA’s New Experimental Antenna Tracks Deep Space Laser where they explain that this laser receiver is used to track the laser light emitted from Psyche, not to decode it.

The 34-meter (112-foot) radio-frequency-optical-hybrid antenna, called Deep Space Station 13, has tracked the downlink laser from NASA’s Deep Space Optical Communications (DSOC) technology demonstration since November 2023. The tech demo’s flight laser transceiver is riding with the agency’s Psyche spacecraft, which launched on Oct. 13, 2023.

The hybrid antenna is located at the DSN’s Goldstone Deep Space Communications Complex, near Barstow, California, and isn’t part of the DSOC experiment. The DSN, DSOC, and Psyche are managed by NASA’s Jet Propulsion Laboratory in Southern California.

“Our hybrid antenna has been able to successfully and reliably lock onto and track the DSOC downlink since shortly after the tech demo launched,” said Amy Smith, DSN deputy manager at JPL. “It also received Psyche’s radio frequency signal, so we have demonstrated synchronous radio and optical frequency deep space communications for the first time.”

A close-up of the optical terminal on Deep Space Station 13 shows seven hexagonal mirrors that collect signals from DSOC’s downlink laser. The mirrors reflect the light into a camera directly above, and the signal is then sent to a detector via a system of optical fiber. NASA/JPL-Caltech