Sky & Telescope - March 2019 - 25
Path of spin
axis over 4 days
Path of
viewing
directions
over 4 days
45°
Ecliptic
Sun
R AY THEON CO MPA N Y
But how does AGIS figure out the distance to stars? Like
any telescope, Gaia - through AGIS - can track parallax:
the tiny apparent looping motion made by a star once a year
that's caused by the spacecraft's moving viewpoint around
the Sun (see page 26). However, the looping motions of stars
in the same part of the sky will be synchronized, making
it impossible to decipher their true distance - only their
parallax relative to one another can be calculated. Gaia gets
around this problem by having two fields of view separated
by a wide angle. "If stars are widely separated on the sky,
their looping motions will be out of sync, causing a variation in their angular separation over the year," explains
Lindegren. "That variation contains the additional information needed to determine the size of the loops and hence the
absolute parallaxes."
By spinning in such a way that both fields pass over the
same stars within a short time, and by registering the stars'
positions multiple times to disentangle a star's real and apparent
motion, AGIS has all the data it
needs to churn out the locations,
drift across the sky, and distance of
all stars at the same time, transforming the night sky jigsaw puzzle
into a living 3D projection of the
known universe.
u MIRROR SPINNING Artist's concept
of Raytheon's rotating space telescope.
Depending on mission requirements, the
entire mirror and platform could rotate together (as shown here), or the mirror could
spin on its own.
Skinny, Light, and Cheap
Turning to the future - please excuse the pun - spinning
could hold the key to far more powerful space telescopes.
Technology company Raytheon has been in discussions
with NASA researchers on developing its Rotating Synthetic
Aperture (RSA) concept. "As a professor of physics said of this
technology, 'If Hubble sees toddler galaxies and the James
Webb Space Telescope will see baby galaxies, RSA will see
embryos,'" explains Raytheon Space Systems Vice President
Wallis Laughrey. "But the best fit for the technology by far
and away is direct imaging of exoplanets."
Curved like a canoe, the primary aperture of the telescope would spin like a wind turbine while taking a series of
images. These pictures would then be combined using complex algorithms to produce a crisp final scene.
Although it would have reduced light-gathering power, a
skinny, 20-meter-long RSA could provide the resolution of a
full 20-m telescope at the cost and
mass of an 8-m scope. This is crucial, because the 6.5-m aperture of
JWST is near the limit of what can
fit into current rocket nose cones.
With NASA's recent cost cap of
between $3 billion and $5 billion
on future space telescopes, ideas
like RSA will be essential for pushing the boundaries of space-based
astronomy and delivering new
insights into our dynamic universe.
¢ BENJAMIN SKUSE is a science
writer based in Somerset, UK.
sk yandtele scope.com * M A RCH 2 019
25
http://www.skyandtelescope.com
Sky & Telescope - March 2019
Table of Contents for the Digital Edition of Sky & Telescope - March 2019
Contents
Sky & Telescope - March 2019 - Cover1
Sky & Telescope - March 2019 - Cover2
Sky & Telescope - March 2019 - 1
Sky & Telescope - March 2019 - Contents
Sky & Telescope - March 2019 - 3
Sky & Telescope - March 2019 - 4
Sky & Telescope - March 2019 - 5
Sky & Telescope - March 2019 - 6
Sky & Telescope - March 2019 - 7
Sky & Telescope - March 2019 - 8
Sky & Telescope - March 2019 - 9
Sky & Telescope - March 2019 - 10
Sky & Telescope - March 2019 - 11
Sky & Telescope - March 2019 - 12
Sky & Telescope - March 2019 - 13
Sky & Telescope - March 2019 - 14
Sky & Telescope - March 2019 - 15
Sky & Telescope - March 2019 - 16
Sky & Telescope - March 2019 - 17
Sky & Telescope - March 2019 - 18
Sky & Telescope - March 2019 - 19
Sky & Telescope - March 2019 - 20
Sky & Telescope - March 2019 - 21
Sky & Telescope - March 2019 - 22
Sky & Telescope - March 2019 - 23
Sky & Telescope - March 2019 - 24
Sky & Telescope - March 2019 - 25
Sky & Telescope - March 2019 - 26
Sky & Telescope - March 2019 - 27
Sky & Telescope - March 2019 - 28
Sky & Telescope - March 2019 - 29
Sky & Telescope - March 2019 - 30
Sky & Telescope - March 2019 - 31
Sky & Telescope - March 2019 - 32
Sky & Telescope - March 2019 - 33
Sky & Telescope - March 2019 - 34
Sky & Telescope - March 2019 - 35
Sky & Telescope - March 2019 - 36
Sky & Telescope - March 2019 - 37
Sky & Telescope - March 2019 - 38
Sky & Telescope - March 2019 - 39
Sky & Telescope - March 2019 - 40
Sky & Telescope - March 2019 - 41
Sky & Telescope - March 2019 - 42
Sky & Telescope - March 2019 - 43
Sky & Telescope - March 2019 - 44
Sky & Telescope - March 2019 - 45
Sky & Telescope - March 2019 - 46
Sky & Telescope - March 2019 - 47
Sky & Telescope - March 2019 - 48
Sky & Telescope - March 2019 - 49
Sky & Telescope - March 2019 - 50
Sky & Telescope - March 2019 - 51
Sky & Telescope - March 2019 - 52
Sky & Telescope - March 2019 - 53
Sky & Telescope - March 2019 - 54
Sky & Telescope - March 2019 - 55
Sky & Telescope - March 2019 - 56
Sky & Telescope - March 2019 - 57
Sky & Telescope - March 2019 - 58
Sky & Telescope - March 2019 - 59
Sky & Telescope - March 2019 - 60
Sky & Telescope - March 2019 - 61
Sky & Telescope - March 2019 - 62
Sky & Telescope - March 2019 - 63
Sky & Telescope - March 2019 - 64
Sky & Telescope - March 2019 - 65
Sky & Telescope - March 2019 - 66
Sky & Telescope - March 2019 - 67
Sky & Telescope - March 2019 - 68
Sky & Telescope - March 2019 - 69
Sky & Telescope - March 2019 - 70
Sky & Telescope - March 2019 - 71
Sky & Telescope - March 2019 - 72
Sky & Telescope - March 2019 - 73
Sky & Telescope - March 2019 - 74
Sky & Telescope - March 2019 - 75
Sky & Telescope - March 2019 - 76
Sky & Telescope - March 2019 - 77
Sky & Telescope - March 2019 - 78
Sky & Telescope - March 2019 - 79
Sky & Telescope - March 2019 - 80
Sky & Telescope - March 2019 - 81
Sky & Telescope - March 2019 - 82
Sky & Telescope - March 2019 - 83
Sky & Telescope - March 2019 - 84
Sky & Telescope - March 2019 - Cover3
Sky & Telescope - March 2019 - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202501
https://www.nxtbook.com/nxtbooks/aas/st_202412
https://www.nxtbook.com/nxtbooks/aas/st_202411
https://www.nxtbook.com/nxtbooks/aas/st_202410
https://www.nxtbook.com/nxtbooks/aas/st_202409
https://www.nxtbook.com/nxtbooks/aas/st_202408
https://www.nxtbook.com/nxtbooks/aas/st_202407
https://www.nxtbook.com/nxtbooks/aas/st_202406
https://www.nxtbook.com/nxtbooks/aas/st_202405
https://www.nxtbook.com/nxtbooks/aas/st_202404_qr
https://www.nxtbook.com/nxtbooks/aas/st_202404
https://www.nxtbook.com/nxtbooks/aas/st_202403
https://www.nxtbook.com/nxtbooks/aas/st_202402
https://www.nxtbook.com/nxtbooks/aas/st_202401_aus
https://www.nxtbook.com/nxtbooks/aas/st_202401
https://www.nxtbook.com/nxtbooks/aas/st_202312_aus
https://www.nxtbook.com/nxtbooks/aas/st_202312
https://www.nxtbook.com/nxtbooks/aas/st_202311
https://www.nxtbook.com/nxtbooks/aas/st_202310
https://www.nxtbook.com/nxtbooks/aas/st_202309
https://www.nxtbook.com/nxtbooks/aas/st_202308
https://www.nxtbook.com/nxtbooks/aas/st_202307
https://www.nxtbook.com/nxtbooks/aas/st_202306
https://www.nxtbook.com/nxtbooks/aas/st_202305
https://www.nxtbook.com/nxtbooks/aas/st_202304
https://www.nxtbook.com/nxtbooks/aas/st_202304_qr
https://www.nxtbook.com/nxtbooks/aas/st_202303
https://www.nxtbook.com/nxtbooks/aas/st_202302
https://www.nxtbook.com/nxtbooks/aas/st_202301
https://www.nxtbook.com/nxtbooks/aas/st_202212
https://www.nxtbook.com/nxtbooks/aas/st_202211
https://www.nxtbook.com/nxtbooks/aas/st_202210
https://www.nxtbook.com/nxtbooks/aas/st_202209
https://www.nxtbook.com/nxtbooks/aas/st_202208
https://www.nxtbook.com/nxtbooks/aas/st_202207
https://www.nxtbook.com/nxtbooks/aas/st_202206
https://www.nxtbook.com/nxtbooks/aas/st_202205
https://www.nxtbook.com/nxtbooks/aas/st_202204
https://www.nxtbook.com/nxtbooks/aas/st_202203
https://www.nxtbook.com/nxtbooks/aas/st_202202
https://www.nxtbook.com/nxtbooks/aas/st_202201
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com