Call me crazy, but I'm worried about the increasing number of "things" in orbit because of my interest in astrophysics, astrophotography, and deep space exploration, both of which require lengthy amounts of clear viewing time for all types of Earth-bound telescopes. Additionally, even the LIGO gravitational wave experiments may be impacted from the electronic noise generated by the sheer numbers of these small satellites whizzing by overhead.
Apart from SpaceX, its rival company OneWeb has also expressed its intent to launch hundreds of its own satellites into space. Like Starlink, OneWeb’s satellites also aim to provide internet service from space.
With thousands of satellites about to launch into space, experts are worried about what would happen if these break down, tumble uncontrollably or burn up in re-entry. Eventually, these tiny spacecraft will end up as so much additional orbiting junk around Earth.
"If things break in space, it's pretty difficult to solve that problem," Tim Farrar, the president of the satellite communications research and consulting firm TMF Associates, told NPR. "It's not like your car breaking down on the side of the road with AAA available to give you a hand."
According to the European Space Agency (ESA), there are about 900,000 pieces of space junk smaller than 10 centimeters in low-Earth orbit. If companies continue to deploy their own satellites into space, this number could soon reach a million or more.
As previous reports have shown, the overcrowding in Earth’s vicinity has become a serious problem. In the autumn of 2019, one of SpaceX’s Starlink units almost collided with an ESA satellite. This fender-bender was avoided after the latter decided to fire up its thrusters to move out of the way.
More recently, the highly touted Satellite Constellations 1 Workshop Report from August of 2020, explained that: Existing and planned large constellations of bright satellites in low-Earth orbit (LEOsats) will fundamentally change astronomical observing at optical and near-infrared (NIR) wavelengths.
Nighttime images without the passage of a Sun-illuminated satellite will no longer be the norm. If the 100,000 or more LEOsats proposed by many companies and many governments are deployed, no combination of mitigations can fully avoid the impacts of the satellite trails on the science programs of current and planned ground-based optical-NIR astronomy facilities.
Astronomers are just beginning to understand the full range of impacts on the impacted disciplines. Astrophotography, amateur astronomy, and the human experience of the stars and the Milky Way are already affected.
The Satellite Constellations 1 (SATCON1) workshop held virtually on 29 June–2 July 2020. SATCON1, organized jointly by NSF’s NOIRLab and AAS with funding from NSF, aimed to quantify better the impacts of LEOsat constellations at optical wavelengths and explore possible mitigations.
Recent technology developments for astronomical research — especially wide-field imaging on large optical telescopes — face significant challenges from the new ability in space and communication technologies to launch many thousands of LEOsats rapidly and economically. This troubling development went unnoticed by our community as recently as 2010, when New Worlds, New Horizons — the most recent National Academies’ decadal survey of astronomy and astrophysics — was issued.
In the last year, the sky has changed, with growing numbers of satellite trails contaminating astronomical images. Many astronomical investigations collect data with the requirement of observing any part of the sky needed to achieve the research objective with uniform quality over the field of view. These include studies that are among the highest priorities in the discipline: stellar populations in the Milky Way and neighboring galaxies; searches for potentially hazardous near-Earth objects; identification of gravitational wave sources such as neutron star mergers; and wide-area searches for
transiting exoplanets. At a minimum, a fraction of the area being imaged is lost to the trails or significantly reduced in the S/N (signal-to-noise ratio).
However, many of these areas of research also include a time-critical aspect and/or a rare, scientifically critical target. Such a missed target, even with low probability, will significantly diminish the scientific impact of the project. For example, if a near-Earth object is not recovered, its orbital parameters are lost. If the transit of a promising super-Earth exoplanet candidate is missed, the orbital timing may not be recovered. If the optical counterpart of a gravitational wave source is lost in the few percent of pixels in satellite trails, its rapid fading may preclude subsequent identification. Detailed simulations beyond the scope of this workshop are required to better quantify the potential scientific cost of losing uniform full area coverage in these cases.
Even more challenging simulations are required to understand the impact on very large samples (e.g., from Vera C. Rubin Observatory*) that are limited not by small number statistics but rather by systematic uncertainties. One measure of precision cosmology, for example, is the gravitational weak lensing shear that elongates faint galaxy images, and more complex modeling is needed to understand the major impact these satellites will have on this field.
Starlink: Getting Internet Everywhere |thespacetechie.com
Initial visibility simulations have shown the significant negative impacts expected from two communications-focused LEOsat constellations, Starlink (launched by Space Exploration holdings, LLC [SpaceX]), and OneWeb. For SATCON1, simulations were performed of the visibility of LEOsats with 30,000 second-generation Starlink satellites below 614 km and ~48,000 OneWeb satellites at 1200 km, in accord with the FCC filings for these projects. For all orbital heights, the visibility of sunlit satellites remains roughly constant between sunset and astronomical twilight (Sun 18 degrees below the horizon). The key difference between lower (~600 km) and higher (~1200 km) orbits is the visibility in the dark of night between astronomical twilights: higher altitude constellations can be visible all night long during summer, with only a small reduction in the number visible compared to those in the twilight.
Star Link satellites posing issues for astronomers/Hackaday
Mitigation of the most damaging impacts on scientific programs is now being actively explored by the professional astronomy community worldwide. These investigations have benefited from collaboration
with SpaceX, the first operator to launch a substantial constellation of LEOsats (538 satellites over 9 launches as of July 2020). Changes are required at both ends: constellation operators and observatories. SpaceX has shown that operators can reduce reflected sunlight through satellite body orientation, Sun shielding, and surface darkening. A joint effort to obtain higher accuracy public data on predicted locations of individual satellites (or ephemerides) could enable some pointing avoidance and mid-exposure shuttering during satellite passage. Observatories will need to adopt more dynamic scheduling and observation management as the number of constellation satellites increases, though even these measures will be ineffective for many science programs.
SATCON1 was attended by over 250 astronomers and engineers from commercial operators (mainly from SpaceX since they are furthest along in their work on this issue), as well as other stakeholders, and reached a number of conclusions and recommendations for future work. The organizers hope that the collegiality and spirit of partnership between these two communities will expand to include other operators and observatories and continue to prove useful and productive. Our findings and recommendations should serve as guidelines for observatories and satellite operators alike to use going forward, even as we work toward a more detailed understanding of the impacts and mitigations.
The impacts of large constellations of LEOsats on astronomical research programs and the human experience of the night sky are estimated to range from negligible to extreme, depending on factors including the scientific or other goals of the observation, the etendue of the facility, the observing strategy and ability to avoid satellites, and the ability to mask or remove satellite trails in data. The impact also depends strongly on the number of satellites, the orbital altitude of the satellites, the apparent brightness and attitude of the satellites, and the accuracy of their positional ephemerides**. Most astronomical researchers and institutions are only now, a little over a year after the first tranche of 60 Starlink satellites were launched, coming to appreciate fully the magnitude and complexity of the problem.
* Vera C. Rubin Large Synoptic Telescope's goal is to conduct the 10-year Legacy Survey of Space and Time (LSST). LSST will deliver a 500 petabyte set of images and data products that will address some of the most pressing questions about the structure and evolution of the universe and the objects in it. The Rubin Observatory LSST is designed to address four science areas:
• Probing dark energy and dark matter.
• Taking an inventory of the solar system.
• Exploring the transient optical sky.
• Mapping the Milky Way.
The scientific questions that Rubin Observatory will address are profound, and yet the concept behind the design of Rubin Observatory is remarkably simple: conduct a deep survey over an enormous area of sky; do it with a frequency that enables images of every part of the visible sky to be obtained every few nights; and continue in this mode for ten years to achieve astronomical catalogs thousands of times larger than have ever previously been compiled.
The construction phase of the project will deliver the facilities needed to conduct the survey: a large-aperture, wide-field, optical imaging telescope; a gigapixel camera; and a data management system.
The 8.4-meter Simonyi Survey Telescope uses a special three-mirror design, which creates an exceptionally wide field of view, and has the ability to survey the entire sky in only three nights. The Rubin Observatory Summit Facility is located on the Cerro Pachón ridge in north-central Chile. The observatory site is inland and approximately 60 m (100 km) by road from the support town of La Serena, where the Rubin Observatory Base Facility is located.
The Rubin Observatory LSST Camera must produce data of extremely high quality with minimal downtime and maintenance. In order to take advantage of high-quality images produced over such a wide field, the camera contains over three billion pixels of solid state detectors.
Software is one of the most challenging aspects of Rubin Observatory, as more than 20 terabytes of data must be processed and stored each night.
See:
https://www.lsst.org/about
** Positional ephemerides - See: Astronomy and Astrophysics, 114, 297-302 (1982)
Orientation of the JPL Ephemerides, DE 200/LE200 to the Dynamical Equinox of J2000
E.M. Standish, Jr.
Jet Propulsion Laboratory/California Institute of Technology, Mail Stop 264/664, 4800 Oak Grove Drive, Pasadena, CA 91109 USA
Received May 18, accepted June 9, 1982
This paper gives a detailed analysis of the computations required to compute the ephemerides of celestial bodies.
Hartmann352
See:
https://exoplanetarchive.ipac.caltech.edu/docs/transit_algorithms.html
See:
https://aas.org/sites/default/files/2020-08/SATCON1-Report.pdf
See:
https://www.ibtimes.com/spacex-star...crease-space-junk-pieces-dramatically-2864145
Hundreds of astronomers, satellite operators, and dark-sky advocates recently joined forces to call out a problem that impacts all three groups: the
petapixel.com
The Milky Way Galaxy above La Silla Observatory | Chile | Britannica.c
Hubble ACS image of the immense galaxy cluster Abell S1063 - showing gravitational lensing
Hubble's Ultra Deep Field - Posted by Earth
I just love looking up at The Milky Way on a clear night, seeing those photos of gravitational lensing and examining photos like Hubble's ultra deep field, which required lengthy viewing times of the same area of space. However, as is indicated above, each side, business and astronomy, whether scientific or amateur, must meet and agree to an enforceable plan to limit the impact of the seeming exponential growth of orbital material, smart or otherwise, on the night sky. Our night time observations and our gravity wave receivers cannot come to a halt due to the impact of micro-satellites. We owe such a plan to all of mankind.
Hartmann352
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