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By Linda Copman, based on an interview with Barbara Schaefer
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| Photo: Barbara Schaefer ponders proposals
from prospective observers who are hoping to reserve
time on the Keck Telescopes. Photo by Gloria Martin,
Keck Observatory. |
Barbara Schaefer is arguably Keck Observatory’s longest-serving
employee. Schaefer started working on Keck-related projects
three years before the project was funded
by the W. M. Keck Foundation.
Schaefer was recruited by Jerry Nelson,
principal designer of the Keck Telescopes, because she had
experience operating large telescopes and because of her experience
on Mauna Kea, one of the proposed sites for the telescope.
After graduating from the University of Wisconsin with a degree
in Astronomy and Physics in 1975, Schaefer spent four years
operating the 4-meter and 2.1-meter telescopes at Kitt Peak
National Observatory in Arizona. In 1979 she made her first
move to Hawai`i Island, where she worked for the NASA Infra-Red
Telescope Facility (IRTF), one of a handful of observatories
on Mauna Kea at that time (now there are thirteen).
With the opening of the Keck II Telescope in 1996, it soon
became apparent that a coordinator was needed to manage the
expanded team of Observing Assistants (OAs) who were needed
to operate both the Keck I and Keck II Telescopes, as well
as to interact with the visiting astronomers before, during,
and after their runs. The position of Observing Support Coordinator
was created, and Barbara Schaefer was promoted to fill this
role. Schaefer has remained in this position for the past 12
years.
Schaefer’s duties can be divided roughly into thirds. One third
of her time is spent hiring, scheduling, and supervising the
OAs. To her credit, during Schaefer’s 12-year tenure as Coordinator,
only a handful of OAs have moved on to new positions, some
of them within the Observatory. Another third of Schaefer’s
time is spent interfacing between the night crew (OAs) and
the day crew to make sure that issues that arise during nightly
observing runs are clearly communicated to and addressed by
the daytime operations crew. And the remaining third of Schaefer’s
time is spent scheduling observing time on the Keck Telescopes
and interacting with the observers.
Schaefer uses multiple spreadsheets and strategies to complete
the daunting task of scheduling, which can take anywhere from
7 to 12 months from start to publication of the final six-month
observing schedule. The two weeks prior to distribution of
the draft schedule is the most intense for Schaefer, and her
colleagues know to steer clear of her during this time. Schaefer
jokes that she hangs a sign on her door which reads, “If you
knock, you better have chocolate.” This year, her colleagues
added a corollary, “The darker the chocolate, the darker the
night.” Dark nights, with less than 32 percent of ambient moonlight,
are at a premium, especially for astronomers who study the
faint objects at the fringes of the universe.
“In reality,” says Schaefer, “I can’t be bribed.” If a night
of observing at Keck Observatory were ever put out to bid on
E-bay, Schaefer believes it would attract high-stakes bidders.
But, of course, this is not how the system works.
The Keck Observatory scheduling system runs more like a well-oiled
clock, with all stakeholders knowing well in advance what to
expect and few last-minute surprises. Planning for the second
semester of 2008, which runs from August 2008 through January
2009, begins in January 2008. The first step is to send out
an internal memo to Keck department heads and administrators,
in order to determine engineering needs for the upcoming semester.
In the early days, from 1994-96, only about half of the available
nights were allocated for science, while half the nights were
reserved for building and testing the telescopes and instruments.
The number of engineering nights has decreased substantially,
so that now only about fourteen to sixteen nights per semester
are set aside for commissioning new instruments, making upgrades
to operations, and repairs and maintenance, such as the rotation
of mirror segments every two years so that individual segments
can be recoated. This means that roughly 10 percent of nights per
year are allocated for telescope and instrument engineering:
the remaining 90 percent of the nights at Keck Observatory are dedicated
to producing science.
“I like solving puzzles and this schedule is
a huge puzzle. You have to put everything in the right
places. For example, what instrument configurations cause
problems? I enjoy the challenge of solving these problems.” — Barbara
Schaefer
The next step in the scheduling process is to establish a chart
of available time indicating the percentage of “dark” time
for each night. “Dark” time is measured by determining what
percentage of each night has no moonlight. The coordinates
of the moon between the evening and morning twilights are used
to determine the relative darkness of each night. The University
of California publishes a Keck
Observing Calendar indicating the percentage of darkness
for each night. The nights are then grouped into “dark” (> 68 percent
of the night has no moonlight), “grey” (between 32 — 68 percent of
the night has no moonlight), or “bright” (< 32 percent of the night
has no moonlight) categories.
Next, the right ascension and declination of the sky over Mauna
Kea are plotted. At different times of year, different stars
are visible in the sky, depending on their east/west (right
ascension) and north/south (declination) coordinates. “Imagine
the Earth is a glass sphere with a light bulb in the center,” explains
Schaefer. “If the light projected the longitude and latitude
lines of the Earth out onto the sky, these lines would define
the right ascension and declination of celestial objects. As
the Earth rotates on its axis and revolves around the Sun,
different right ascension and declination coordinates are visible
from our location on the planet.”
This is of key importance to astronomers who wish to observe
scientific targets that may only be visible during certain
months of the year. For example, the galactic center is only
visible from Keck Observatory from late April through July
2008. Another important consideration is the local sidereal
time (LST), or the time according to the stars. The LST is
four minutes per night different than Earth’s 24-hour clock.
By calculating the LST midway through each night, one can determine
which stars will be directly overhead midway through that night.
All of these factors — the LST, right ascension and declination
coordinates, and darkness rating — are critically important
to astronomers in determining when the optimum times to schedule
their observations will be.
For example, for cosmologists who study faint galaxies at the
far reaches of our universe, dark time is crucial. The visible
wavelengths emitted by these targets are so faint that they
must be observed when the moon is down and the night is more
than 68 percent free of moonlight. On the other hand, certain instruments
that measure infrared wavelengths are not adversely affected
by moonlight, so observations utilizing these instruments can
be scheduled on bright nights with more moonlight. In the first
semester of 2008 there are 182 nights, and roughly one third
of these nights are dark (58 nights), one third are grey (56
nights), and one third are bright (68 nights).
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| Image: A sample table showing the percent
darkness, right ascension (RA) and declination (Dec),
and local sidereal time (LST) for some of the nights
in the first semester of 2008. Table courtesy of Barbara
Schaefer. |
Schaefer compiles a “time available” chart, identifying how
many of each kind of night there are in each month in the semester.
After subtracting out the engineering nights, she then begins
the complicated process of allocating nights among the various
partner institutions. The University of Hawai`i (UH) gets 10 percent
of available nights on the Keck I Telescope and 15 percent of available
nights on the Keck II Telescope. Keck Observatory’s Director
is awarded one night per month, spread evenly between dark,
grey, and bright nights over the course of the semester. NASA
has one-sixth of however many nights remain after UH and the
Director get their cuts. For the first semester of 2008, the Telescope
System Instrumentation Program (TSIP) was awarded four
nights on each telescope; this allocation varies by semester
and TSIP will receive eight nights on each telescope in the
second semester of 2008. Together, these four constituencies
(UH, Director, NASA, and TSIP) account for roughly one-third
of all the available nights. The remaining two-thirds of the
available nights are divided between Caltech and the University
of California. Each partner’s total number of nights is carefully
divided into thirds, so that everyone gets some dark, some
grey, and some bright nights.
One final piece of the puzzle is the specifications for the
various instruments available at the Observatory. For example,
the interferometer (IF) uses both telescopes together for the
entire night, and these nights are typically scheduled first
to ensure that both telescopes are available on the same nights.
Certain instruments occupy the same focal position on the telescope,
and time must be allocated between scheduling these instruments
to allow for them to be physically exchanged. Staff limitations
also come into play, since special expertise is required to
operate the laser guide star adaptive optic systems, for example.
Other factors which must be considered include scheduled upgrades
to a particular instrument, which could take that instrument
out of commission for a week or more. Partner institutions
are notified of any specific limitations or additions to instrument
availability — along with their time allocations for the upcoming
semester. The percent dark table, time available chart, and
instrumentation specifications are sent to each of the partner
institutions, with instructions to “spread their time as evenly
as possible over the semester.”
Four to five months prior to the start of the upcoming semester,
the Time Allocation Committees (TACs) at each institution accept
proposals for observing time from their respective constituencies.
The TACs utilize a peer review process to rate the incoming
proposals. Most institutions receive many times more proposals
than can be accommodated in the available time, so the TACs
play a critical role in reviewing and ranking the various proposals.
All proposals that the TACs deem worthy of telescope time are
sent to Schaefer along with a suggested time table for accommodating
the highest ranking proposals.
“On May 1 and November 1, I close my door,” says Schaefer.
Schaefer then compiles a draft schedule by placing all of the
observers into time slots on a master spreadsheet. When conflicts
arise, Schaefer often emails the affected partner institutions
to get their input on adjusting the schedule to accommodate
everyone’s needs. About two and a half months prior to the
start of the new semester, Schaefer sends the finished draft
out to the partner institutions and the executive staff of
the Observatory for final approval. They respond with suggested
changes, if any, and two months prior to the start of the semester, the
schedule is posted online. The final step is to assign
support astronomers (SAs) and observing assistants (OAs) for
each night — a step that is completed about one month prior
to the start of the semester.
The majority of applicants are research and/or teaching staff
at the partner institutions, and, of course, there is a high
percentage of returning observers over the years. UC is increasingly
awarding half nights to different observing teams, in order
to maximize time on the Keck Telescopes, since some objects
are only visible in the sky for half the night. Schaefer estimates
that between 1300 and 1400 individuals have observed at Keck
Observatory over the years, and she is now compiling a photographic
log of each of the individual observers. The number of PIs
(Principal Investigators or those scientists actually granted
time for their proposals) is smaller than 1300-1400. The larger
numbers apply to those who have actually come observing and
include the PIs, their graduate students, and others collaborating
on projects. In FY07, 397 astronomers observed on the Kecks.
For the past few semesters, UC and Caltech have traded a very
few Keck Observatory nights for nights at the neighboring Gemini
and Subaru telescopes. This practice allows researchers shared
access to unique facilities and instruments at the neighboring
observatories. In return, scientists who generally use Gemini
and Subaru are able to make use of the unique instruments at
Keck Observatory.
Other extraneous factors that may impact the schedule for a
particular night are called “targets of opportunity.” These
are transitory cosmic events such as an exploding comet or
a gamma
ray burst that occur randomly during times the telescopes
have already been scheduled for other projects. When such events
occur, the scheduled astronomer may receive a phone call from
an off-site colleague to request that the telescope be redirected
to observe the opportunistic phenomena. “This happens a couple
of nights per semester,” reports Schaefer.
Trading nights is also possible amongst observers if all necessary
parameters are met. Schaefer has the final say on such trades,
and she carefully reviews all proposed changes to the published
schedule prior to authorizing changes. Unanticipated changes
occur when disasters like the October 2006 earthquake or 9/11
happen. Blizzards can also shut down the Observatory, or bad
weather can cause an observer to resort to contingency plans
for observing alternate targets with alternate instruments
that are less impacted by weather conditions. Unfavorable weather,
broken instruments, and disasters also result in time lost — and
no allowance is made for such events. Observers impacted by
such events may reapply for time in a subsequent semester,
but there are no guarantees.
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| Photo: Barbara Schaefer celebrates the
successful completion of another semester’s schedule.
Photo by Gloria Martin. |
Because time on the Keck Telescopes is so precious, the scientists
who observe at Keck almost always do their observing on-site.
When scientists are on-site, they are able to make instantaneous
decisions about where to look in the sky, what to focus on,
and what to focus on as a backup target in case of technical
difficulties. This dynamic decision-making generates robust
science and optimizes the scientific output of the Keck Telescopes.
Other telescopes which rely on a computerized scheduling system
sacrifice the human ingenuity factor which is so significant
at Keck Observatory.
“Scientists like to be able to make decisions
on the fly and do their own science. At Keck, our scientists
are intimately involved in doing science 100 percent of their
time here.” — Barbara Schaefer 
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