Thruster Firings Boost Healthy TESS Planet Hunter over Halfway to Final Science Orbit Prior to Critical May 17 Lunar Flyby: Interview

Artist’s concept of NASA’s Orbital
ATK-built
Transiting
Exoplanet Survey Satellite (
TESS) planet
hunting satellite orbiting the Earth-Moon system. Credit: NASA/Orbital ATK

Ken Kremer     SpaceUpClose.com     13 May 2018

KENNEDY SPACE
CENTER, FL – NASA’s recently launched TESS planet hunting probe is healthy,
operating very well, and more than halfway through the demanding regimen of on
board thruster firings required to carry out the preplanned series of six orbit
raising maneuvers setting up this weeks do or die Lunar Flyby trajectory
adjustment on May 17 – absolutely critical to reaching its intended science perch,
Orbital ATK TESS program manager Robert Lockwood told
SpaceUpClose.com in an interview.
The goal of TESS is to carry out an
all sky survey and discover dozens of new Earth and Super Earth sized
exoplanets beyond our Solar System that may be capable of supporting life, and
possibly answer one of humanities most profound questions – “Are We Alone?”

“Everything is as expected with the spacecraft systems,” Orbital ATK TESS program manager
Robert Lockwood told SpaceUpClose.com in an exclusive interview.
  Lockwood is based at the TESS mission
operations center at Orbital ATK headquarters in Dulles, VA. 
“We are all green. We have done four of the six [orbit
raising and adjustment] thruster firing maneuvers.” 
Then
we have the flyby of the Moon on Wednesday night /early Thursday May 17 … that
will change the orbit significantly .. 
and get in position    … to do a
period adjustment to get into the special ‘goldilocks’ orbit – the P/2 lunar
resonant orbit.”
P/2 is the name of the TESS missions final science orbit. 
The lunar flyby takes place at 06:31:52.180
UTC on 17 May 2018 at a distance of approximately 8000 kilometers altitude
above the surface.
“We are very excited about the lunar flyby!” gushed
Lockwood.

NASA’s TESS Exoplanet hunter being processed by
technicians inside the Payload Hazardous Servicing Facility clean room on Feb
20, 2018 at the Kennedy Space Center.  Launch on SpaceX Falcon 9 occurred
on April 18, 2018. Credit: Ken
Kremer/SpaceUpClose.com/kenkremer.com
The $240 million spacecraft was
built by prime contractor Orbital ATK.
TESS is NASA’s second exoplanet
mission and a follow up to the hugely successful Kepler probe which discovered
over 2300 exoplanets of all sizes. 

The TESS spacecraft systems are in excellent health and the
engineering and science teams are diligently working through the middle of the
commissioning phase activities. 
“Everything is clicking off per planned so far in the
commissioning timeline,” Lockwood told me. 
“The science phase will begin on June 12!”
The kitchen table sized probe weighs
770 pounds (350 g) and measures 12 x 4 x 5 ft (3.7 x 1.2 x 1.5 m).

Roughly 1 month after the beautiful
sunset blastoff to space from the Florida Space Coast on April 18 aboard a
SpaceX Falcon 9 rocket NASA’s newest exoplanet
hunting spacecraft is in fine shape and on course to achieve its very special
mission enabling P/2 lunar resonant orbit. 

NASA’s
next planet-hunter, the Transiting Exoplanet Survey Satellite (TESS),
successfully launched on a SpaceX Falcon 9 rocket on
April 18, 2018 from Space Launch Complex-40 on Cape Canaveral Air Force Station,
FL – in this view from a pad camera. TESS will search for new worlds
outside our solar system for further study.
  Credit:
Ken Kremer/kenkremer.com/spaceupclose.com
The Transiting Exoplanet
Survey Satellite (TESS) successfully blasted off on a two stage SpaceX Falcon 9
rocket at 6:51 p.m. EDT, April 18, from seaside Space Launch Complex-40 on Cape
Canaveral Air Force Station, Florida.

After liftoff TESS uses
six thruster burns to travel in a series of progressively elongated orbits to
reach the Moon – which will provide a gravitational assist so that TESS can
transfer into its 13.7-day P/2 lunar resonant final science orbit – a highly
elliptical orbit around Earth.


Graphic of NASA’s
Transiting Exoplanet Survey Satellite orbit raising maneuvers. Credit: NASA
After approximately 60
days of check-out and instrument testing, the spacecraft will begin its important
work.

What is the current
spacecraft status?

“We are all green. We finished all spacecraft checkouts at
L plus 5 days after launch,” Lockwood explained.
Describe
the spacecraft checkout? Is everything going as planned?
“Yes everything is clicking off per planned so far in the
commissioning timeline.”
“We took about 5 days to check out all the basic spacecraft
functionalities including power, thermal control, attitude control, propulsion,
etc.” 
Thus the spacecraft systems checkout has concluded.
“So then we turned TESS over to the instrument team. That’s
primarily to do their part to check out the cameras and make the measurements
they want to make on orbit.”
The four
cameras were powered on on April 30.
They were slowly cooled
to their operating temperature of -85°C.

How long will the camera checkout require?
“There is plenty of time for checkouts of the science
instrument. We have about 7 weeks until we are in the final science orbit.”
To carry out its daunting task, the
spacecraft is equipped with 4 identical wide-field science cameras.  Their combined field of view will enable the
spacecraft to image some 85% of the entire sky during the full sky survey over
the first two years of the primary mission phase. 

Each of the four cameras is equipped
with four 16.8 megapixel CCD’s and a seven element optical system. 

The cameras are located on the top
of the kitchen table sized spacecraft inside a protective sunshade to shield
the instruments.

As part of the calibration phase the
cameras were collecting data as of May 9. 

So the
camera check-out phase has started! 

Please describe the six orbit raising thruster maneuvers
and lunar flyby? 
“There were a series of maneuvers to get in position to fly
by the Moon and then do a period adjustment to get into the special
‘goldilocks’ orbit, P/2 lunar resonant orbit,” Lockwood explained. 
“We have done four of the six thruster
firing [orbit raising] maneuvers.”
“First
we did a calibration maneuver 3 days after launch. Then we raised the apogee to
the level of the moon about a week after launch.”
“Then
we did a small timing adjustment maneuver about 2 weeks after.”
The
first two firings were called the first apogee maneuver (A1M) and the first
perigee maneuver (P1M) and were conducted on 22 and 25 April respectively. 
A1M
was a 50 second checkout burn to characterize the performance of the
TESS thrusters.
“Then
we have what’s called a B plane targeting maneuver to get to a specific spot to
flyby the moon – [completed Sunday].”
“Then
we have the flyby of the Moon Wednesday night/early Thursday May 17.”
“Then
in 3 weeks time we have the period adjust maneuver to get into the P/2 orbit.”
“Then
we go through one P/2 orbit for commissioning.”
“After
that we begin the science phase in the P/2 orbit on June 12. 
It’s all gone very well.” 
Describe the impact on the mission and how important is the
lunar flyby?
“The lunar flyby will change the orbit significantly.  That’s really part of the whole elegance of
the mission design. The lunar flyby will put us in an orbit that’s inclined to
the ecliptic by about 35 degrees,” Lockwood stated.
“It will also raise our Perigee up to double the distance
of GEO. So we’ll be at about 17 Earth radii for the perigee and 70 Earth radii
for the apogee.”
“The we will do the period adjust maneuver after that to
lower the apogee to about 59 Earth radii.”
“That period adjust maneuver which lasts about 15 minutes
will put TESS in exact resonance with the Moon.” 
“We are very excited about the lunar flyby!”
Will any science be collected during the lunar flyby?
“No science will by gathered during the flyby.”

Watch this video explaining the orbit raising maneuvers:


Video Caption:  TESS Orbit Insertion 1.  Credit: NASA

Can you describe the engine firings in detail?

“The thruster firings are typical delta V maneuvers using
one central delta V thruster on the spacecraft,” Lockwood elaborated. 
“The largest maneuver was the apogee raising maneuver. It
lasted 449 seconds and that raised the apogee from 275,000 km to 350,000 km.”
“The short 7 second timing maneuver [P2M or Perigee 2 Maneuver], and 26
second targeting maneuver were both very short firings.”
“The other substantial maneuver is the period adjust maneuver,
after we have flown past the moon [lunar flyby]. It will be about a 15 minute
burn on May 30.” 
Describe the thruster? 
“We do these all with the one main delta V engine which is
a 22 newton thruster.”
What is TESS current orbit now?
“We are currently in the highly eccentric phasing orbit,
which has an apogee of 350,000 km. So its out at the distance to the moon about
57 Earth radii.  The perigee is about 800
km altitude.” 
When does the spacecraft become operational and the science
begin? 
“The first science orbit starts on June 12 – which is in
about 7 weeks.”

“The spacecraft will be declared operational on June 12-
when the science gathering begins.”
But before that, the entire team will conduct a thorough mission
checkout review.

“The team will conduct a post launch assessment review at NASA
Goddard in Maryland on June 4 of the spacecraft, instruments and associated
ground systems. They will check that all three of those elements are ready to
proceed into mission operations.”

The
Falcon 9 launch itself went extremely well and injected TESS into its intended
orbit using so little fuel that the science gathering can go on for “decades”
if the spacecraft survives.

Spacecraft
checkout began soon after launch.

Just how good was the launch injection and propellent fuel
usage?
“The launch was very accurate to 1 sigma accuracy. We
needed only 1/3 of the fuel on board,” Lockwood told me.

“So there is enough fuel on board for many decades of use!”

“It is good enough for decades of operation.” 
“Everything is as expected with the spacecraft systems. It’s
all gone very well.”

NASA’s
next planet-hunter, the Transiting Exoplanet Survey Satellite (TESS),
successfully launched on a SpaceX Falcon 9 rocket on
April 18, 2018 from Space Launch Complex-40 on Cape Canaveral Air Force Station,
FL – in this view from a pad camera. TESS will search for new worlds
outside our solar system for further study.
  Credit:
Ken Kremer/kenkremer.com/spaceupclose.com
The SpaceX Falcon 9 delivered TESS
to the highly elliptical Earth orbit never used before by a science mission, said George Ricker, TESS principal investigator at the
Massachusetts Institute of Technology’s (MIT) Kavli Institute for Astrophysics
and Space Research in Cambridge
Ricker at a prelaunch media
briefing.

TESS will orbit Earth in 13.7 days
in a 2:1 resonance orbit with the moon. The moon orbits earth every 28 days.
The TESS science orbit is extremely
stable as a result, thus requiring minimal fuel to maintain.  The spacecraft was intentionally loaded with
enough propellants to continue its observations for 20 years or more if all
goes well with the spacecraft systems.  

During those hoped
for decades of exploration, TESS will search for new Earths beyond the confines
of our Solar System on a first-of-its-kind mission to
find worlds that could potentially support life. 
TESS is
expected to find thousands of new exoplanets orbiting nearby stars.

Scientists plumbing the data
gathered by TESS hope to discover on the order of 300 to 500 Earths and Super
Earths alone, orbiting in their habitable zones compared to a dozen or so by
Kepler.

TESS observations will yield the
orbits and sizes of these exoplanets. 
They will also provide the specific targets for follow up high
resolution investigations by NASA’s James Webb Space Telescope and other telescopes
to determine the exoplanets masses, compositions and atmospheric constituents. 

In turn researchers will use these observations
to determine if any of the newly discovered Earths and Super Earths are actually Earth-like possessing water, oxygen and carbon based molecules for
example that can potentially support life.

“We are thrilled TESS is on its way to help us
discover worlds we have yet to imagine, worlds that could possibly be
habitable, or harbor life,” said Thomas Zurbuchen, associate administrator of
NASA’s Science Mission Directorate in Washington, in a statement. 
“With missions like the James Webb Space
Telescope to help us study the details of these planets, we are ever the closer
to discovering whether we are alone in the universe.”
 “One
critical piece for the science return of TESS is the high data rate associated
with its orbit,” said Ricker in a statement. “Each
time the spacecraft passes close to Earth, it will transmit full-frame images
taken with the cameras. That’s one of the unique things TESS brings that was
not possible before.”
For this two-year survey mission, scientists
divided the sky into 26 sectors. TESS will use its four unique wide-field
cameras to map 13 sectors encompassing the southern sky during its first year
of observations and 13 sectors of the northern sky during the second year,
altogether covering 85 percent of the sky.
TESS is a NASA
Astrophysics Explorer
mission led and operated by MIT and managed by
Goddard. George Ricker, of MIT’s Kavli Institute for Astrophysics and Space
Research, serves as principal investigator for the mission. TESS’s four
wide-field cameras were developed by MIT’s Lincoln Laboratory. Additional
partners include Orbital ATK, NASA’s Ames Research Center, the
Harvard-Smithsonian Center for Astrophysics, and the Space Telescope Science
Institute. More than a dozen universities, research institutes and
observatories worldwide are participants in the
mission.
Watch for Ken’s continuing onsite coverage of NASA’s TESS,
SpaceX, ULA, Boeing, Lockheed Martin, Orbital ATK and more
space and mission
reports direct from the Kennedy Space Center and Cape Canaveral Air Force
Station, Florida.
Stay tuned here for Ken’s continuing
Earth and Planetary science and human spaceflight news: www.kenkremer.com –www.spaceupclose.com –
twitter @ken_kremer –
ken
at kenkremer.com


Ken Kremer/SpaceUpClose with the TESS spacecraft inside the Payload Hazardous Servicing Facility clean room
on Feb 20, 2018 at the Kennedy Space Center.  Launch on SpaceX Falcon 9
occurred on April 18, 2018. Credit: Ken
Kremer/SpaceUpClose.com/kenkremer.com

Up close
view of
NASA
TESS exoplanet hunter encapsulated inside the nose cone atop SpaceX Falcon 9
rocket poised for liftoff from Space Launch Complex-40 on Cape Canaveral Air
Force Station, FL, on April 18.
Credit: Ken Kremer/kenkremer.com/spaceupclose.com

Ken Kremer

Watch for Ken’s continuing onsite coverage of NASA, SpaceX, ULA, Boeing, Lockheed Martin, Northrop Grumman and more space and mission reports direct from Kennedy Space Center and Cape Canaveral Air Force Station in Florida and Wallops Flight Facility in Virginia. Stay tuned here for Ken's continuing Earth and Planetary science and human spaceflight news. Dr. Kremer is a research scientist and journalist based in the KSC area, active in outreach and interviewed regularly on TV and radio about space topics. Ken’s photos are for sale and he is available for lectures and outreach events.

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