WASHINGTON — Two senators have asked the U.S. Government Accountability Office to review the Federal Communications Commission’s decision to exempt satellite constellations like SpaceX’s Starlink from an environmental review, given those satellites’ effect on the night sky.In an April 2 letter to Comptroller General Gene Dodaro, Sens. Tammy Duckworth (D-Ill.) and Brian Schatz (D-Hawaii) asked the GAO to examine the FCC’s decision, made decades ago, to not subject satellite systems seeking FCC licenses from environmental assessments.
The letter is not the first to question the FCC’s exemption of satellite systems from NEPA. In January, a paper by a Vanderbilt University law student attracted attention by arguing that the categorical exemption was inappropriate and that the FCC could be sued in federal court to overturn it.While that paper garnered attention, astronomical organizations haven’t seriously considered going to court. “In all my discussions with the leadership of the AAS, there’s never been any interest in going down this path,” said Joel Parriott, director of public policy at the American Astronomical Society (AAS), during a March 31 meeting of the National Academies’ Committee on Astronomy and Astrophysics. “I’m not spending any time or energy worrying about it.”He and other astronomers, during a committee discussion about the effects of Starlink and other satellite constellations on astronomy, emphasized they preferred working with companies to try and mitigate the effects of the satellites on observations. “The key here is partnership, not confrontation,” Parriott said.
New filinghttps://fcc.report/IBFS/SAT-MOD-20200417-00037QuoteSpace Exploration Holdings, LLC seeks to modify its Ku/Ka-band NGSO license to relocate satellites previously authorized to operate at altitudes from 1,110 km to 1,325 km down to altitudes ranging from 540 km to 570 km, and to make related changes.
Space Exploration Holdings, LLC seeks to modify its Ku/Ka-band NGSO license to relocate satellites previously authorized to operate at altitudes from 1,110 km to 1,325 km down to altitudes ranging from 540 km to 570 km, and to make related changes.
This is actually big news. SpaceX proposes to have all of its constellation below 600 km. The 1000 km+ layers were, as shown in my study, a problem for optical asrtonomy. This will mean fewer illuminated satellites during the middle of the night, good news for us.
Cross-posting:Quote from: TorenAltair on 04/18/2020 01:42 amNew filinghttps://fcc.report/IBFS/SAT-MOD-20200417-00037QuoteSpace Exploration Holdings, LLC seeks to modify its Ku/Ka-band NGSO license to relocate satellites previously authorized to operate at altitudes from 1,110 km to 1,325 km down to altitudes ranging from 540 km to 570 km, and to make related changes.
SUMMARYLastly, while many were excited after SpaceX’s first launches, some in the optical astronomy community voiced concern that the light reflected from those satellites could interfere with their space observations. While the Commission does not have jurisdiction over the visibility of satellites, SpaceX is committed to promoting all forms of space exploration, which is why it has already taken a number of proactive steps to ensure it does not materially impact optical astronomy. SpaceX is working with U.S. and international astronomy organizations and observatories to measure scientifically the actual impact of its satellites. Within weeks of receiving results back from these tests—and as a result of SpaceX’s unique ability to quickly update, manufacture, and launch its satellites—SpaceX deployed an experimental darkening treatment on one in-orbit satellite to further reduce the visibility on the body of the satellites. Beyond this treatment, SpaceX is developing new mitigation efforts that it plans to test in the coming months. Additionally, SpaceX will make satellite tracking data available so astronomers can better coordinate their observations with our satellites. These measures, along with SpaceX’s work with leading astronomy groups, will enable SpaceX to bring the substantial benefits of broadband access to underserved populations around the world without materially impacting views of the night sky.Despite some claims to the press, operating at higher orbits does not alleviate the need for operators to take additional steps to mitigate their impact on optical astronomy—in fact, higher orbits may worsen the effect in some cases. SpaceX therefore encourages other satellite operators to engage in similar active steps to study their effects on astronomy. Together, the satellite industry and optical astronomers can ensure the public reaps the benefits of satellites operations while mitigating the impact on space exploration.
.@elonmusk: The goal of @SpaceX is to make Starlink satellites "invisible to the naked eye within a week of launch". Also notes that the brightness of the objects is directly related to their configuration/orientation on orbit, which they continue to work on. #Astro2020
.@elonmusk What the public sees is mostly the #Starlink objects during orbit raise. Once the objects reach station, the source of brightness is the reflection from antennas. We tried blacking out the antennas on Darksat and it worked, but sun shades will work better. #Astro2020
.@elonmusk, in response to a question from the #Astro2020 WG: We support a regulatory framework that requires satellite operators to keep object brightness "within limits that don’t fundamentally inhibit science." #Starlink
@elonmusk: Soon all Starlink objects launched will be modeled on "Visorsat", which uses a radio-transparent foam material as a sun shade. They should be less visible from the ground. How we roll them during orbit raise may also reduce visibility. #Astro2020
I will say that this presentation by @elonmusk for #Astro2020 includes the most detailed view of the Starlink satellites I have yet seen. He's reiterating the point about the goal of Starlink to not yield an impact to science.
.@elonmusk: We're interested in replacing the earliest Starlink sats we launched as the tech progresses. We expect the 1st generation sats to be replaced on a timescale of 3-4 years. We do not want 'ancient electronics' in orbit like GEO sats up there for 15, 20 years. #Astro2020
.@elonmusk reiterates: "If there’s any situation where we’re impeding science, we will take corrective action." #Starlink #Astro2020
SpaceX' writeup for the above presentation is now online.
"Starlink has three phases of flight: (1) orbit raise, (2) parking orbit (380 km above Earth), and (3) on-station (550 km above Earth). During orbit raise the satellites use their thrusters to raise altitude over the course of a few weeks. [...] Once satellites are on-station they reconfigure so the antennas face Earth and the solar array goes vertical so that it can track the Sun to maximize power generation. [...] Currently, about half of the over 400 satellites are on-station and the other half are orbit raising or in the parking orbit. [...]It's important to note that at any given time, only about 300 satellites will be orbit raising or parking (unclear whether this is for the full constellation or the initial one - if for the full constellation, numbers estimated in this thread by me and others were quite off in a negative sense)"
"When Starlink satellites are orbit raising, they roll to a limited extent about the velocity vector for power generation, always keeping the cross sectional area minimized while keeping the antennas facing Earth enough to stay in contact with the ground stations.[...] When the satellites reach their operational orbit of 550 km, the attitude control system is able to overcome this drag with the solar array raised above the satellite in a vertical orientation that we call "shark-fin."
Diffuse reflections are the biggest contributor to observed brightness on the ground, because diffuse reflections go in all directions[...]The biggest contributors to Starlink being bright are the white diffuse phased array antennas on the bottom of the satellite, the white diffuse parabolic antennas on the sides, and the white diffuse back side of the solar array (Highly contested points, by some in this very thread, just a few months ago)While in orbit raise and the parking orbit the solar array dominates due to the much larger surface area. However, once the satellites are at their operational altitude, the antennas dominate because the bright backside of the solar array is shadowed.
DarkSat [...] darkened the phased array and parabolic antennas designed to tackle on-station brightness. This reduced the brightness of the satellite by about 55%, as was verified by differential optical measurements comparing DarkSat to other nearby Starlink satellites. This is nearly enough of a brightness reduction to make the satellite invisible to the naked eye while on-station. However, black surfaces in space get hot and reflect some light (including in the IR spectrum), so we are moving forward with a sun visor solution instead. This avoids thermal issues due to black paint (It was likewise contested that thermal issues would be significant, while they prompted the DarkSat solution to be abandoned.)
We're currently testing rolling the satellite so the vector of the Sun is in-plane with the satellite body, i.e. so the satellite is knife-edge to the Sun.[...]However, there are a couple of nuanced reasons why this is tricky to implement:1- rolling the solar array away from the Sun reduces the amount of power available to the satellite.2- because the antennas will sometimes be rolled away from the ground, contact time with the satellites will be reduced.3- the star tracker cameras are located on the sides of the chassis (the only place they can go and have adequate field of view). Rolling knife edge to the Sun can point one star tracker directly at the Earth and the other one directly at the Sun, which would cause the satellite to have degraded attitude knowledge.(The array's "pivot axis" doesn't allow it to roll along its long axis, just to cant it towards/away from the satellite body, limiting the amount of useful light reflection mitigation to a one-time maneuver when transitioning out of low-drag mode. Special, and onerous, full-satellite maneuvers need to be implemented - again a very contested point earlier this year.)
we designed an RF-transparent deployable visor for the satellite that blocks the light from reaching most of the satellite body and all of the diffuse parts of the main body. [...]Not only does this approach avoid the thermal impacts from surface darkening the antennas, but it should also have a larger impact on brightness reduction. As previously noted, the first VisorSat prototype will launch in May and we will have these black, specular visors on all satellites by June.(Sounds like a much stronger plan, although as was expectable a much larger change in design, plus it will be interesting to see if it's really that RF-transparent - kudos for going for that and implementing it in all sats launched while testing it (vs DarkSat's solution), regardless of its final effectiveness.)
Any visualizations of these sun visors out yet? I seem to be having trouble thinking what it would look like.
At the end of April SpaceX stated:QuoteMaking the satellites generally invisible to the naked eye within a week of launch. We're doing this by changing the way the satellites fly to their operational altitude, so that they fly with the satellite knife-edge to the Sun. We are working on implementing this as soon as possible for all satellites since it is a software change.That change has been implemented, at least for two trains at 380km. Last night (14th May 21:40GMT) the L1.3 train was dark passing south of UK. The previous roll-angle mode would have presented the full face of the sunlit panel to me, but nothing was seen of the complete train (naked-eye). This morning (15th May 01:30GMT) the L1.4 train was observed, again to the south, this time with binoculars. The full face of the sunlit panel should have been visible, but all objects apart from one were magnitude ~4.5, so they were just naked-eye visible, but not prominent.So apart from the first week of each mission (as stated in the quote) the days of bright Starlink trains are over, as SpaceX promisedThe panel is edge on to the Sun, but not edge on to the observer so I was seeing the panels at glancing angles of 26 and 13 degrees, respectively, but the panel surface is dark and sunlight reflection is just from the edge of the panel. The mode would only be used when the Starlinks could be observer from the ground, a relatively small part of the orbit, and would revert to the Sun-pointing mode at other times, but exceptions are noted in that SpaceX report.The one exception on the L1.4 train was SL-1235 which was the full, bright magnitude 1 object that would have been expected with the previous roll-control mode.I did not seek to observe Starlinks that are under power on the way up to 550km to see if they were using the same knife-edge mode, but those objects are always more scattered, not in a tight train.edit: 1300GMT 15th May - corrected typo, L1.3 and L1.4 trains were observed
Making the satellites generally invisible to the naked eye within a week of launch. We're doing this by changing the way the satellites fly to their operational altitude, so that they fly with the satellite knife-edge to the Sun. We are working on implementing this as soon as possible for all satellites since it is a software change.
I think a thing a lot of people don’t realize is that engineers really like solving problems. The more challenging it is, the greater the pleasure once it’s solved.
In an #AAS236 press conference, Pat Seitzer of the Univ. of Michigan shows what OneWeb’s new 48,000-satellite proposal would mean for observations at the Rubin Obs. in Chile. Hundreds of satellites would be visible all night long in summer.
Worth keeping in mind, though, that the chance that this 48,000-satellite gets launched is very low, especially since OneWeb is in Chapter 11 right now.
Both Seitzer and James Lowenthal of Smith College emphasize SpaceX is doing a good job trying to mitigate the effects of Starlink; other satellite operators, though, have not engaged with astronomers about similar mitigation efforts.
That is a good presentation. I am curious about the OneWeb satellites. It seemed like they implied OneWeb will de-orbit satellites that are taken out of service. Satellites that die before that would take 'centuries' to decay, if I recall the presentation correctly.I thought Greg had indicated that satellites taken out of service would go into a graveyard orbit? I don't know if that plan also applies to the extra 48,000 that were applied for but if so is anyone concerned about that? How long does it take to decay from this graveyard orbit?
