A Shroud of Satellites

The first five Iridium satellites were launched on May 5, 1997, and by 2002 there were 66 operational satellites, providing consistent global satellite phone coverage. These satellites have the interesting property that their antenna panels sometimes reflect sunlight down to the Earth’s surface, causing what came to be known as “Iridium flares”, delighting terrestrial observers—myself included. During an Iridium flare event, the satellite suddenly appears and gradually brightens and then dims to invisibility as it moves slowly across a section of sky over several seconds. Many of these events reach negative magnitude, with some getting as bright as magnitude -9.5.

The next generation of Iridium satellites began launching in 2017, but these satellites are constructed in such a way that they do not produce flares. Gradually, the original Iridium satellites are de-orbiting (or being de-orbited), so eventually there will be no more Iridium flares.

The Iridium flares haven’t been much of a nuisance to astronomers because the number of events per night for a given observer have been in the single digits.

But now we’re facing too much of a good thing. The first volley of 60 Starlink satellites was launched on May 24, with 12,000 expected to be in orbit by 2028. These satellites will provide broadband internet service to the entire planet. Though the Starlink satellites aren’t expected to produce spectacular flares like the first generation of the Iridium satellites, they do reflect sunlight as any satellite does, and the sheer number of them in relatively low Earth orbit is sure to cause a lot of headaches for astronomers and stargazers throughout the world.

I estimate that about 468 of the 12,000 satellites will be above your horizon at any given moment, but how many of them will be visible will depend on their altitude (both in terms of distance above the Earth’s surface and degrees above the horizon), and where they are relative to the Earth’s shadow cone (they have to be illuminated by sunlight to be seen).

And Starlink will not be the only swarm of global broadband internet satellites, as other companies and countries plan to fly their own satellite constellations.

This situation illustrates yet another reason why we need a binding set of international laws that apply to all nations and are enforced by a global authority. The sooner we have this the better, as our survival may depend upon it. How else can we effectively confront anthropogenic climate change and the precipitous decline in biodiversity?

As for these swarms of satellites, two requirements are needed now to minimize their impact on astronomy:

  1. Build the satellites with minimally reflective materials and finishes
  2. Fly one internationally-managed robust constellation of global broadband internet satellites, and require competing companies and nations to utilize them, similar to the co-location often required for terrestrial communication towers

I’d like to close this piece with a few questions. Will future “stargazers” go out to watch all the satellites and generally ignore the real stars and constellations because they are too “boring”? Will professional astronomers increasingly have to move their operations off the Earth’s surface to the far side of the Moon and beyond? Will we continue to devalue the natural world and immerse ourselves ever more deeply into our human-invented virtual environments?

Satellite, Meteor, and Aircraft Crossings 2018

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but since October 4, 1957 another “species” of sky vermin made their debut: artificial satellites.  In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my ~¼° field of view.

I’ve put together a video montage and some individual videos of satellites I’ve recorded between March 10, 2018 and November 24, 2018.  All of the events are shown below, with the boldface events being presented chronologically in the first video.  Both the NORAD and International designations are given for each satellite.  The range is the distance between observer and satellite at the time of observation.

UT Date
3-10-2018
3-25-2018
4-1-2018
4-2-2018
5-5-2018
7-6-2018
7-26-2018
7-31-2018
8-3-2018
8-23-2018
9-16-2018
10-21-2018 (2 satellites)
10-24-2018

Target Star
UCAC4 459-002239
TYC 621-45742-1
UCAC4 497-035454
UCAC4 416-092784
UCAC4 385-061427
N Sct 2018
UCAC4 429-110724
UCAC4 384-149264
UCAC4 362-194694
UCAC4 526-007192
UCAC4 316-210974
UCAC4 418-144100
UCAC4 302-215969

Satellite
SL-8 RB (Kosmos 726)
unknown space debris
unknown satellite
unknown satellite
unknown satellite
Ariane 5 RB (Payload A)
SL-8 RB (Kosmos 726)
Ariane 5 RB (VA209)
YURI 2A (BS-2A)
Kosmos 1092
SL-8 RB (Kosmos 80)
Galaxy 17 & NIMIQ 6
Sentinel 1B

Satellite
SL-8 RB (Kosmos 726)
unknown space debris
unknown satellite
unknown satellite
unknown satellite
Ariane 5 RB (Payload A)
SL-8 RB (Kosmos 726)
Ariane 5 RB (VA209)
YURI 2A (BS-2A)
Kosmos 1092
SL-8 RB (Kosmos 80)
Galaxy 17
NIMIQ 6
Sentinel 1B

Designation
7737; 1975-028-B
unknown
unknown
unknown
unknown
27946; 2003-043-B
7737; 1975-028-B
38780; 2012-051-C
14659; 1984-005-A
11326; 1979-030-A
1575; 1965-070-F
31307; 2007-016-B
38342; 2012-026-A
41456; 2016-025-A

Range & Direction
2,199.9 km SE
unknown SE
unknown SE
unknown NE
unknown NE
34,141.7 km NE
1,483.2 km SE
18,153.7 km NE
39,042.5 km NE
1,870.9 km NE
3,137.8 km NE
37,737.7 km E
37,736.3 km E
2,028.6 km NW

You’ll notice that sometimes the satellite crosses the field as a moving “dash”. That’s because sometimes I used longer exposure times to record a fainter target star.  A wind gust hit the telescope during the second event (3-25-2018).  The field is oriented North up and East to the left.  In this first video, you’ll notice that Sentinel 1B (the last event) has a unusual retrograde orbit (sun-synchronous) and is moving towards the NW.

In general, the slower the satellite is moving across the field, the higher is its orbit around the Earth.  One must also consider how much of the satellite’s orbital motion is along your line of sight to the satellite.

In the following video clip, you’ll see an unidentified piece of space debris, a very faint “dash” (due to integration) moving NE across the field from lower right to upper left, recorded on May 5, 2018 UT.

Next, we see a Ariane rocket body used to hoist SMART-1 towards the Moon and the Insat 3E and eBird 1 towards their geostationary orbits.  This recording was made on July 6, 2018 UT.  The rocket body is traveling NE (mostly east).  The light curve below the video suggests the possibility of some tumbling motion, but the satellite is faint and the photometry noisy.

And here is a rapidly tumbling (but low amplitude) Ariane rocket body, observed on July 31, 2018 UT and traveling NE.

Here is a no-longer-operational Japanese communications satellite named Yuri 2A, launched in 1984 and captured here on August 3, 2018 UT.  It is traveling NE (mostly east) and shows a beautiful long-period large-amplitude light curve.

Finally, we see not one but two geostationary communication satellites, Galaxy 17 (first and fainter) and NIMIQ 6 moving east across the field (as my telescope tracks westward to follow the Earth’s rotation), captured here on October 21, 2018 UT.  Galaxy 17 exhibits no discernible rotation, but NIMIQ 6 shows a low-amplitude long-period change in brightness.

Next we turn to three telescopic meteors I recorded on June 4, July 7, and September 11, 2018 UT.

UT Date
6-4-2018
7-7-2018
9-11-2018

Target Star
UCAC4 408-094611
UCAC4 275-188730
UCAC4 399-093188

Constellation & Direction
Scutum, SSE
Sagittarius, SW
Scutum, NNE

Here these meteors are presented in a video montage.

I even captured an airplane crossing the field on August 22, 2018 UT:

References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21