{"id":146059,"date":"2025-11-21T07:52:18","date_gmt":"2025-11-21T07:52:18","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/146059\/"},"modified":"2025-11-21T07:52:18","modified_gmt":"2025-11-21T07:52:18","slug":"a-us-start-up-plans-to-deliver-sunlight-on-demand-after-dark-can-it-work-monash-lens","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/146059\/","title":{"rendered":"A US start-up plans to deliver \u2018sunlight on demand\u2019 after dark. Can it work? \u2013 Monash Lens"},"content":{"rendered":"\n

A proposed constellation of satellites has astronomers very worried. Unlike satellites that reflect sunlight and produce light pollution<\/a> as an unfortunate byproduct, the ones by US startup Reflect Orbital<\/a> would produce light pollution by design.<\/p>\n

The company promises to produce \u201csunlight on demand\u201d with mirrors that beam sunlight down to Earth so solar farms can operate after sunset<\/a>.<\/p>\n

It plans to start with an 18-metre test satellite named Earendil-1 that the company has applied to launch in 2026<\/a>. It would eventually be followed by about 4000 satellites in orbit by 2030, according to the latest reports<\/a>.<\/p>\n

So how bad would the light pollution be? And perhaps more importantly, can Reflect Orbital\u2019s satellites even work as advertised?<\/p>\n

Bouncing sunlight \"Sunlight<\/a> Sunlight can be bounced off a wristwatch to produce a spot of light. Photo: M. Brown, CC-BY-SA \u00a0 <\/p>\n

In the same way you can bounce sunlight off a watch face to produce a spot of light, Reflect Orbital\u2019s satellites would use mirrors to beam light onto a patch of Earth.<\/p>\n

But the scale involved is vastly different. Reflect Orbital\u2019s satellites would orbit about 625km above the ground, and would eventually have mirrors 54 metres across<\/a>.<\/p>\n

When you bounce light off your watch onto a nearby wall, the spot of light can be very bright. But if you bounce it onto a distant wall, the spot becomes larger \u2013 and dimmer.<\/p>\n

This is because the sun is not a point of light, but spans half a degree in angle in the sky. This means that at large distances, a beam of sunlight reflected off a flat mirror spreads out with an angle of half a degree.<\/p>\n

What does that mean in practice? Let\u2019s take a satellite reflecting sunlight over a distance of roughly 800km \u2013 because a 625km-high satellite won\u2019t always be directly overhead, but beaming the sunlight at an angle. The illuminated patch of ground would be at least 7km across.<\/p>\n

Even a curved mirror or a lens can\u2019t focus the sunlight into a tighter spot due to the distance and the half-degree angle of the sun in the sky.<\/p>\n

Would this reflected sunlight be bright or dim? Well, for a single 54-metre satellite it will be 15,000 times fainter than the midday sun, but this is still far brighter than the full moon.<\/p>\n

\"An<\/a> Mylar reflectors can be unfolded in orbit. Image: Josh Spradling\/The Planetary Society, CC-BY \u00a0 The balloon test <\/p>\n

Last year, Reflect Orbital\u2019s founder, Ben Nowack,\u00a0posted a short video<\/a> that summarised a test with the \u201clast thing to build before moving into space\u201d. It was a reflector carried on a hot air balloon.<\/p>\n

In the test, a flat, square mirror roughly 2.5 metres across directs a beam of light down to solar panels and sensors. In one instance the team measures 516 watts of light per square metre while the balloon is at a distance of 242 metres.<\/p>\n

For comparison, the midday sun produces roughly 1000 watts per square metre. So 516 watts per square metre is about half of that, which is enough to be useful.<\/p>\n

However, let\u2019s scale the balloon test to space. As we noted earlier, if the satellites were 800km from the area of interest, the reflector would need to be 6.5km by 6.5km \u2013 42 square kilometres. It\u2019s not practical to build such a giant reflector, so the balloon test has some limitations.<\/p>\n

So what is Reflect Orbital planning to do? <\/p>\n

Reflect Orbital\u2019s plan is \u201csimple satellites in the right constellation shining on existing solar farms\u201d. And their goal is only 200 watts per square metre<\/a> \u2013 20% of the midday sun.<\/p>\n

Can smaller satellites deliver? If a single 54-metre satellite is 15,000 times fainter than the midday sun, you would need 3000 of them to achieve 20% of the midday sun. That\u2019s a lot of satellites to illuminate one region.<\/p>\n

Another issue is that\u00a0satellites at a 625km altitude move at 7.5 kilometres per second. So a satellite will be within 1000km of a given location for no more than 3.5 minutes.<\/p>\n

This means 3000 satellites would give you a few minutes of illumination. To provide even an hour, you\u2019d need thousands more.<\/p>\n

Reflect Orbital isn\u2019t lacking ambition. In one interview, Nowack suggested 250,000 satellites<\/a> in 600km high orbits. That\u2019s more than all the currently catalogued satellites<\/a> and large pieces of space junk put together.<\/p>\n

And yet, that vast constellation would deliver only 20% of the midday sun to no more than 80 locations at once, based on our calculations above. In practice, even fewer locations would be illuminated due to cloudy weather.<\/p>\n

Additionally, given their altitude, the satellites could only deliver illumination to most locations near dusk and dawn, when the mirrors in low Earth orbit would be bathed in sunlight. Aware of this, Reflect Orbital plans for its constellation to encircle Earth above the day-night line<\/a> in sun-synchronous orbits<\/a> to keep them continuously in sunlight.<\/p>\n

\"A<\/a> Cheaper rockets have enabled the deployment of satellite constellations. Photo: SpaceX\/Flickr, CC BY-NC \u00a0 Bright lights <\/p>\n

So, are mirrored satellites a practical means to produce affordable solar power at night? Probably not. Could they produce devastating light pollution<\/a>? Absolutely.<\/p>\n

In the early evening it doesn\u2019t take long to spot satellites and space junk \u2013 and they\u2019re not deliberately designed to be bright. With Reflect Orbital\u2019s plan<\/a>, even if just the test satellite works as planned, it will sometimes appear far brighter than the full moon.<\/p>\n

A constellation of such mirrors would be devastating to astronomy and dangerous to astronomers. To anyone looking through a telescope, the surface of each mirror could be almost as bright as the surface of the sun, risking permanent eye damage<\/a>.<\/p>\n

The light pollution will hinder everyone\u2019s ability to see the cosmos, and light pollution is known to impact the daily rhythms of animals<\/a> as well.<\/p>\n

Although Reflect Orbital aims to illuminate specific locations, the satellites\u2019 beams would also sweep across Earth when moving from one location to the next. The night sky could be lit up with flashes of light brighter than the moon.<\/p>\n

The company did not reply to questions\u00a0regarding these concerns within deadline. However, it recently told Bloomberg<\/a>\u00a0it plans to redirect sunlight in ways that are \u201cbrief, predictable and targeted\u201d, avoiding observatories and sharing the locations of the satellites so scientists can plan their work.<\/p>\n

The consequences would be dire <\/p>\n

It remains to be seen whether Reflect Orbital\u2019s project will get off the ground. The company may launch a test satellite, but it\u2019s a long way from that to getting 250,000 enormous mirrors constantly circling Earth to keep some solar farms ticking over for a few extra hours a day.<\/p>\n

Still, it\u2019s a project to watch. The consequences of success for astronomers \u2013 and anyone else who likes the night sky dark \u2013 would be dire.<\/p>\n

\"The<\/p>\n

This article was originally published on The Conversation<\/a>, and was co-authored with Matthew Kenworthy, associate professor in astronomy at Leiden University.<\/p>\n","protected":false},"excerpt":{"rendered":"A proposed constellation of satellites has astronomers very worried. Unlike satellites that reflect sunlight and produce light pollution…\n","protected":false},"author":2,"featured_media":146060,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[98056,98061,35173,98063,35171,35172,111,139,98059,69,98054,98058,98055,16610,147,98057,13670,98062,98060],"class_list":{"0":"post-146059","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-artificial-sunlight","9":"tag-artificial-sunlight-from-space","10":"tag-faculty-science","11":"tag-mirror-satellites-for-solar-farms","12":"tag-monash-lens","13":"tag-monash-university","14":"tag-new-zealand","15":"tag-newzealand","16":"tag-night-sky-pollution","17":"tag-nz","18":"tag-reflect-orbital","19":"tag-satellite-constellation","20":"tag-satellite-light-pollution","21":"tag-satellites","22":"tag-science","23":"tag-space-mirrors","24":"tag-space-technology","25":"tag-space-based-solar-power","26":"tag-sunlight-on-demand"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/146059","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=146059"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/146059\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/146060"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=146059"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=146059"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=146059"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}