Sky & Telescope - March 2020 - 19

Orbital altitude at perigee and apogee (km)

Starlink by the Numbers:
Brightness and Visibility
600
operational altitude

500

400

300

44240

44250

44260

44270

44280

44290

44300

Satellite catalog number

p HOW HIGH? Observations from the SeeSatL group contributed to this plot of the altitudes
of the Starlink satellites, current as of press
time. Fifty Starlink satellites are at an operational altitude of 550 km (dark blue). The ten
satellites lower than 550 km are marked light
blue. Two of these are intentionally deorbiting,
and three more stopped communicating with
ground stations and will deorbit naturally.

p STARLINKED On the morning of November 18th, newly launched Starlink
satellites flying at 280 km crossed over the Dark Energy Camera, which is mounted
on the 4-meter Blanco Telescope at the Cerro Tololo Inter-American Observatory
in Chile. The six-minute exposure of the outskirts of the Large Magellanic Cloud
was designed to look for new dwarf galaxies in the Milky Way's vicinity but instead
recorded the passage of the Starlink train. These satellites will spread out and fade
somewhat in a matter of weeks - but they will still affect professional exposures.

Initial Constellations

Final Constellations

Jan. 2020

Visual magnitude

Feb.
Mar.
4

April
May
June

July
S44282
S44247

S44268

Sept.
44240

44250

44260

44270

44280

44290 44300

Satellite catalog number
PLOTS: LE A H TISCIONE / S&T; SOURCE: JON ATH A N
MCDOWELL (2); STARLINK TR AILS: DELV E SURV E Y, CTIO /
AUR A / NSF; SATELLITE VISIBILIT Y: G REGG DINDER M A N / S&T;
SOURCE: CEES BASSA

Aug.

S44286

Oct.
Nov.

p HOW BRIGHT? SeeSat-L contributors Jay
Respler, Brad Young, Bram Dorreman, and
Ron Lee observed Starlink satellites in July
and August 2019, when the majority of the first
batch of Starlink satellites had reached 550 km.
Those at lower altitudes are marked light blue;
satellites with no measurements are marked
with vertical lines. Most measurements cluster
around magnitude 6, the limiting magnitude for
a rural site, and well within range of naked-eye
viewing at a truly dark-sky site.

Dec.
18h
0

21h

10
20
30
40
Number of sunlit satellites

18h
50

21h

40 60 80 100 120 140
Number of sunlit satellites

p HOW VISIBLE? The numbers of megaconstellation satellites visible in the night
sky are plotted for an observer at latitude 40°N, with darker squares representing
more satellites. The charts show satellite density for a given time of day (horizontal
axis) and time of year (vertical axis). Left: Here's what could be in store by the end
of 2020, assuming initial constellations of 1,584 Starlink satellites and 648 OneWeb
satellites. Right: Future satellite visibility is based on FCC filings, with 11,927 Starlinks, 1,980 OneWeb satellites, and 3,236 Kuiper satellites. The edge of the plot
marks sunset and sunrise, while the interior black line marks astronomical twilight.
sk yandtelescope.org * MARCH 2 02 0

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Sky & Telescope - March 2020

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