Amazon is set to launch two satellites on Friday, in its first test mission as part of its plan to deliver the internet from space and compete with Elon Musk's Starlink service.

The launch window for the Atlas V rocket from the United Launch Alliance (ULA) hub at Kennedy Space Center in Florida is scheduled to open for two hours at 2:00 pm local time (1800 GMT).

Once up and running, the company founded by Jeff Bezos says its Project Kuiper will provide "fast, affordable broadband to unserved and underserved communities around the world," with a constellation of more than 3,200 satellites in low Earth orbit (LEO).

Euclid has found its "lost" guide stars as a software patch has solved its navigation woes and the next six years of observation schedules have been redesigned to avoid stray sunlight: it's the end of an interesting commissioning phase and Euclid will now undergo its final testing in full "science mode.

Our planet is being continuously bathed in radio signals from satnav satellites—which are useful for much more than just navigation. Dedicated space missions acquire these signal reflections to amass valuable environmental information. The shoebox-sized PRETTY CubeSat, flying on Europe's next Vega launcher, will investigate a new frequency and novel observation angle to better measure the rate of climate change—at the same time as gathering radiation data on its surrounding space environment.

The PRETTY, Passive REflecTometry and dosimeTrY, mission will peer ahead to the horizon to receive signals from Global Navigation Satellite System (GNSS) satellites visible just above it. Two patch antennas on its forward face will pick up the same signal from the same satellite—or rather one signal that has reached it through space and the equivalent signal that has reflected off Earth's cryosphere or oceans.

Using a highly advanced version of "spot the difference" PRETTY will compare the twin signals onboard to derive ice and sea height to an accuracy of at least 50 cm from 550 km orbital altitude.

Solar panel technology has advanced significantly in recent years, to the point where solar energy is the fastest-growing renewable power source. The solar panels we have today are a by-product of those used in space.

If you want to power a satellite or crewed spacecraft, there are only two ways: solar energy or nuclear power. Of the two, only solar energy isn't limited by the amount of fuel you bring on board. As we contemplate traveling to other star systems, this raises the question: will solar panels work near other stars?

Solar panels generate an electric voltage through what is known as the photoelectric effect. The effect was first discovered in the 1800s when scientists noticed that charged metallic planets could give off electrons when exposed to ultraviolet light. This led to the discovery that light consisted of quantum particles known as photons.

Missions to the moon, missions to Mars, robotic explorers to the outer solar system, a mission to the nearest star, and maybe even a spacecraft to catch up to interstellar objects passing through our system. If you think this sounds like a description of the coming age of space exploration, then you'd be correct.

At this moment, there are multiple plans and proposals for missions that will send astronauts and/or probes to all of these destinations to conduct some of the most lucrative scientific research ever performed. Naturally, these mission profiles raise all kinds of challenges, not the least of which is propulsion.

Simply put, humanity is reaching the limits of what conventional (chemical) propulsion can do.