There is some indirect evidence that Arecibo's loss has already impacted communication with some of the deep space probes.
NASA's official statement on Arecibo says this:
NASA’s Goldstone Observatory in California, another planetary radar, recently returned to full operations after successful delivery and testing of a new klystron tube for its high-power transmitter. Radars such as those at Goldstone and Arecibo are used only to characterize known NEOs, not to discover previously unknown asteroids and comets, so NASA’s NEO search efforts are not impacted by the planned decommissioning of Arecibo’s 305m radio telescope.
NASA's FAQ on planetary defense from asteroids does not appear to be updated for Arecibo's loss. However, it does credit Arecibo with ruling out an impact in 2029:
Radar observations can reduce the uncertainly in position of an asteroid from the several thousands of kilometers provided by optical observations to just a few meters. The impact risk posed by a potentially hazardous asteroid can be relatively quickly resolved with radar observations, while it might otherwise remain uncertain for years if only optical observations are available. Such was the case with the asteroid Apophis, discovered in 2004 and initially thought to pose a risk of Earth impact in April 2029. Radar observations made by Arecibo Observatory in 2005 eliminated that possibility of impact.
It also reports that radar analysis of near-Earth objects was 1/3 of Arecibo's budget:
The Near-Earth Object Observations Program provides $4.5 million a year in funding to the Arecibo Observatory in Puerto Rico – about one third of the observatory’s yearly budget – to fund its planetary radar capability. The National Science Foundation is in the process of transitioning the Arecibo Observatory to the University of Central Florida and UCF’s proposed alternative funding avenues while reducing NSF’s own level of support. NASA has agreed to continue to fund planetary radar capability at Arecibo during this transition. NASA also uses planetary radar capability at its own Deep Space Network Goldstone station. However, Goldstone’s radar is not as powerful as Arecibo’s, so it does not have the same range into space, meaning that fewer NEOs could be characterized by radar.
With the loss of Arecibo, Goldstone's DSS-14 now becomes the world's largest and most powerful radar dish. (China's 500 meter FAST dish is larger, but has no transmitter and is purely passive.) Sky and Telescope reports that "Arecibo offered 18 times the sensitivity of other existing facilities, such as NASA's Goldstone receiver." It also states
Arecibo is also irreplaceable for scientists. Even though it’s technically the second-largest radio dish in the world (China’s Five-hundred-meter Aperture Spherical Telescope, or FAST, recently broke the record Arecibo held for decades), the observatory has unique capabilities, among them its radar. “FAST cannot do radar, it’s specifically incapable of doing active observation,” Springman explains. Because of that, FAST can’t take Arecibo’s place in planetary defense by characterizing asteroids and their orbits.
It sounds like a significant amount of Goldstone's DSS-14 time will be shifted away from its Deep Space Network duties, and instead put on Near Earth Object radar duty. The 70 meter dishes of the other two DSN sites may also be similarly conscripted to NEO duty. In particular, the tracking schedule for the Canberra DSN site shows considerable changes:
- In the past, the large 70 meter DSS-43 dish (the largest in the southern hemisphere) was used almost daily to contact Voyager 1, Voyager 2, or New Horizons. It now has only four contacts scheduled over the next two months: one with Voyager 1, two with Voyager 2, and one with the Solar Parker Probe.
- Voyager 1 has no other scheduled contacts with Canberra. This is probably because VGR1 is above the ecliptic, but Canberra is in the southern hemisphere.
- Voyager 2 has 113 more scheduled contacts with Canberra, using the smaller dishes, usually in a pair of dishes.
- New Horizons has 10 more scheduled contacts with Canberra, using the smaller dishes.
So there is evidence that some of the communications with the farthest-out spacecraft have been bumped down to the smaller dishes.