| MISSION_DESCRIPTION |
The following material was adapted from the EPOXI mission web site.
Mission Overview
================
EPOXI, a Mission of Opportunity for the NASA Discovery program, is the
combination of two independently proposed scientific investigations
utilizing the Deep Impact (DI) flyby spacecraft as an extended mission:
EPOCh (Extrasolar Planet Observation and Characterization) and DIXI
(Deep Impact eXtended Investigation).
From 22 January through 31 August 2008, EPOCh took advantage of the
permanent on-orbit defocus of the High Resolution telescope (HRI) by
using the High Resolution Visible CCD (HRIV) to collect over 172,000
usable, photometric-quality, visible light images of eight known
transiting planet systems (hot Jupiters): HAT-P-4, HAT-P-7, GJ 436,
TrES-2, TrES-3, XO-2, XO-3, and WASP-3. Time series of continuous
50-second integrations in a subframe mode of 128x128 or 256x256 pixels
with the clear #6 optical filter extending from 350 to 1000 nanometers
were used to observe each system for about three weeks, typically
covering five or more transits as well as secondary eclipses. An
exception is XO-3 which was observed only briefly before the spacecraft
unexpectedly entered safe mode. The transiting planet systems were
observed in the integrated light of the planet and star; no spatially
resolved image of the planet was possible. The out-of-focus HRI
telescope defocuses the images to about 10 pixels or 4 arcseconds at
full-width half-max and introduces visible structure. Each target
series was typically bracketed by a set of dark and internal stimulator
lamp frames to monitor changes in the HRIV CCD detector for calibration
purposes.
On 18-19 March, 28-29 May, and 4-5 June 2008, EPOCh also observed Earth
with the HRIV CCD and the High Resolution Infrared Imaging Spectrometer
(HRII) to characterize it as an analog for extrasolar planets. The
observations comprised imaging in seven optical narrow-band (100
nanometer) filters and 2- to 5-micron infrared spectroscopy over a full
Earth rotation. The optical images used a 512x512-pixel subarray of
the HRIV CCD detector at a scale of about 0.4 arcsec/pixel, and each
frame of the HRII spectrometer was 512 (wavelength) by 128 pixels
(spatial, 2 arcsec/pixel). HRIV CCD images were acquired once every
hour with three filters centered on 350, 750 and 950 nanometers and
once every 15 minutes with the 450-, 550-, 650- and 850-nanometer
filters. Infrared spectra were obtained twice per hour by scanning the
slit of the HRII spectrometer over the earth, using three scans to
ensure coverage of the entire disk; the slit was aligned perpendicular
to the terminator during the scans. The spacecraft orbit was
approximately in the plane of the ecliptic which provided an equatorial
view of Earth with about 62 to 77 percent of the disk illuminated. Each
of the three Earth observing periods lasted approximately 24 hours.
During the 29 May observation, the Moon transited Earth as seen from
the spacecraft (0.3 AU from Earth).
EPOCh continued observations in 2009. These included Earth at both
northern and southern latitudes using the same sequence from 2008.
Additionally that same sequence was used to observe Mars with the
HRII and HRIV instruments in November 2009. On 5-8 October 2009, EPOCh
continuously imaged the exoplanet microlensing event MOA-2009-BLG-266
by reusing the sequence from the HRIV exoplanet transit observations
in 2008.
DIXI consisted of a flyby of comet 103P/Hartley 2 in November 2010 to
study a second comet with the same set of instrumentation as was used by
the Deep Impact mission during the encounter with comet 9P/Tempel 1 in
July 2005. Closest approach to 103P/Hartley 2 occurred at 13:59:47.31
UTC on 4 November 2010 at a distance of 694 km and a flyby speed of
12.3 km/s. The spacecraft flew under the comet on a slightly northward
trajectory in an ecliptic reference frame, then rotated to keep the
body-mounted instruments pointed at the comet for departure imaging.
Over 100,000 visible images and IR spectra of 103P/Hartley 2 were taken,
beginning on 5 September, 60 days before encounter, and continuing
through 26 November 2010, three weeks after the flyby.
103P/Hartley 2 passed perihelion on 28 October, only seven days before
DIXI flyby, and was known to be more active than comet 9P/Tempel 1.
Since the DIXI encounter occurred at a smaller heliocentric distance
than Deep Impact, the project realized a significant improvement to
the signal-to-noise ratio of all visible and IR measurements.
Finally various in-flight calibrations were performed throughout the
EPOXI mission, from October 2007 to February 2011.
Mission Phases
==============
The EPOXI mission has five main phases: Cruise 1, EPOCh, Cruise 2,
DIXI/Hartley 2 Encounter, and Cruise 3. Most phase include several
events or activities. The timeline for the mission and description
of the phases and events are described below.
Mission Timeline
----------------
Phases and Events Start Date/DOY Stop Date/DOY
------------------------------------ -------------- --------------
Cruise 1 2007-09-26/269 2008-01-21/021
Spacecraft Wakeup 2007-09-26/269 2007-09-26/269
Instrument Checkout 2007-10-04/277 2007-10-04/277
EPOCh Photometry Test 2007-11-04/308 2007-11-09/313
Instrument Checkout Retest 2007-12-04/338 2007-12-04/338
HRIV Scattered Light Calibration 2007-12-17/351 2007-12-17/351
Lunar Calibration 2007-12-29/363 2007-12-29/363
Earth Flyby #1 2007-12-31/365 2007-12-31/365
Standard Cruise Calibration 2008-01-09/009 2008-01-09/009
HRII Dark Retake for Lunar Cal 2008-01-16/016 2008-01-17/017
EPOCh 2008-01-22/022 2008-08-31/244
Exoplanet Transit Observations 2008-01-22/022 2008-08-31/244
Earth Observations (#1) 2008-03-18/078 2008-03-19/079
(#4) 2008-05-28/149 2008-05-29/150
(#5) 2008-06-04/156 2008-06-05/157
Standard Cruise Calibration 2008-06-23/175 2008-06-25/177
Cruise 2 2008-09-01/245 2010-09-02/245
HRII Reciprocity Test 2008-09-18/262 2008-09-18/262
HRII Dark Flush Test 2008-09-26/270 2008-09-26/270
HRII Encounter Darks Rerun 2008-10-02/276 2008-10-02/276
HRII Dark Gap Test 2008-10-08/282 2008-10-08/282
Interplanetary Internet Test 2008-10-15/289 2010-11-15/319
HRIV PSF Calibration 2008-12-17/352 2008-12-17/352
Earth Flyby #2 2008-12-29/364 2008-12-29/364
HRII Subframe Gain Calibration 2009-01-26/026 2009-01-26/026
EPOCh Earth North Pole 2009-03-27/086 2009-03-28/087
HRII Lunar Radiometry & Flats 2009-06-01/152 2009-06-02/153
HRII Lunar Rad. & Antisat Filter 2009-06-09/160 2009-06-09/160
HRII Linearity Calibration 2009-06-18/169 2009-06-18/169
Distant Earth Flyby #1 2009-06-29/180 2009-06-29/180
EPOCh Earth South Pole #1 (partial) 2009-09-27/270 2009-09-28/271
Checkout after HRI Turnoff 2009-09-30/273 2009-09-30/273
HRIV Mechanical Checkout 2009-10-01/274 2009-10-01/274
EPOCh Earth South Pole #2 (full) 2009-10-04/277 2009-10-05/278
EPOCh Microlensing MOA-2009-BLG-266 2009-10-05/278 2009-10-08/281
HRII Radiometric Cal #1 (Beta Hyi) 2009-10-13/286 2009-10-24/297
HRII Dark Subframe Test 2009-11-20/324 2009-11-20/324
EPOCh Mars 2009-11-20/324 2009-11-21/325
HRII Lunar Flats/Radiometric Cal #1 2009-12-05/339 2009-12-05/339
HRII Lunar Flats/Radiometric Cal #2 2009-12-12/346 2009-12-12/346
HRII Lunar South Pole Radiometry 2009-12-18/352 2009-12-18/352
Distant Earth Flyby #2 2009-12-28/362 2009-12-28/362
Standard Cruise Calibration 2010-02-16/047 2010-02-16/047
HRII NoSave Flush Test 2010-04-20/110 2010-04-20/110
HRII Radiometric Cal #2 (Beta Hyi) 2010-05-03/123 2010-05-17/137
Earth Flyby #3 2010-06-27/178 2010-06-27/178
MRI Dosido Fast Slew Test 2010-07-12/193 2010-07-12/193
DIXI/Hartley 2 2010-09-03/246 2010-11-28/332
HRIV PSF Calibration 2010-09-03/246 2010-09-03/246
Approach Imaging 2010-09-05/248 2010-11-03/307
E-60 to E-50 days (VIS only) 2010-09-05/248 2010-09-15/258
E-50 to E-40 days (VIS only) 2010-09-15/258 2010-09-25/268
HRII Spectrometer Cooldown 2010-09-25/268 2010-10-01/274
Pre-Encounter Standard Cruise Cal 2010-09-28/271 2010-09-29/272
E-34 to E-8 days (Start HRII) 2010-10-01/274 2010-10-27/300
E-8 days to E-18 hours 2010-10-27/300 2010-11-03/307
Encounter Imaging 2010-11-03/307 2010-11-06/310
E-18 hours to E+2 days 2010-11-03/307 2010-11-06/310
Flyby and Closest Approach 2010-11-04/308 2010-11-04/308
Departure Imaging 2010-11-06/310 2010-11-26/330
E+2 to E+12 days 2010-11-06/310 2010-11-16/320
E+12 to E+21 days 2010-11-16/320 2010-11-26/330
Post-Encounter Standard Cruise Cal 2010-11-27/331 2010-11-28/332
Cruise 3 2010-11-29/333 2011-02-06/037
HRII 50-Frame Extended Linear. Cal 2011-02-05/036 2011-02-06/037
----------------------------------------------------------------------
Cruise 1
--------
Start Time : 2007-09-26 (DOY 269)
Stop Time : 2008-01-21 (DOY 021)
Spacecraft Wakeup and Instrument Checkout
-----------------------------------------
After 25 months in hibernation, the Deep Impact spacecraft was
woken on 26 September 2007. The spacecraft functioned as
expected. On 4 October 2007, the HRII (High Resolution Infrared
Imaging Spectrometer), HRIV (High Resolution Visible CCD), and
MRI (Medium Resolution Visible CCD) instruments were turned on
for the first time in more than two years. A brief checkout
test was performed and confirmed the mechanical components were
functioning. The three science instruments exhibited nominal
behavior of background levels although several HRII detector
pixels had a different response when compared to Deep Impact.
After checkout, several Trajectory Correction Maneuvers (TCM)
were performed in November and December 2007 to alter the
trajectory of the spacecraft to put it on course to flyby the
Earth for a gravity-assist to reach comet 103P/Hartley 2 in 2010.
EPOCh Photometry Test
---------------------
On 4-9 November 2007, EPOCh photometry tests were performed.
During these tests, the HRIV instrument observed a bright (V=9)
visual binary star (HD 80607) for 12 continuous hours to check
pointing and photometric stability. The observations were taken
using the 256-by-256 sub-array mode of the HRIV CCD. The
spacecraft successfully captured the star images and held them on
the sub-array for the full duration of the test. However the
images were unexpectedly offset by about 59 microradian (12.2
arcsec). This was due to stellar aberration which was not
included for stellar observations during the Deep Impact mission.
After correcting for aberration, the spacecraft pointing was
within specifications.
Instrument Checkout Retest
--------------------------
Instrument Checkout Retest: On 4 December 2007 a retest of the
October instrument checkout sequence was performed for the three
science instruments. The focus of this retest was to determine
if HRII pixels that had an odd response during checkout had
changed or improved.
HRIV Scattered Light Calibration
--------------------------------
On 17 December 2007, a calibration for scattered light using
Earth's moon was performed for the HRIV instrument. Many of these
images were obtained with the moon outside but near the field of
view of the HRIV CCD to allow analysis of the amount of light that
is scattered into the field of view from bright objects just
outside or within the field of view.
Lunar Calibration and Earth Flyby #1
------------------------------------
On 29 December 2007, as the spacecraft approached Earth, the HRIV,
HRII, and MRI instruments used the Moon as a target to acquire
data for recalibration purposes. Due to a minor error in the
lunar calibration sequence, a series of HRII dark frames were not
recorded. A retest to acquire the missing HRII darks was
scheduled for 16 January 2008. At 19:29:20.66 UTC on 31 December
2007, the flyby spacecraft achieved its closest approach to Earth
at an altitude of only 15,567.63 km above eastern Asia.
Standard Cruise Calibration
---------------------------
On 9 January 2008, the first of the standard cruise calibrations
for the HRII, HRIV, and MRI instruments was performed. The
calibration sequence included observations of several standard
stars, both solar analogs and hot stars with few absorption lines
in their spectra for absolute calibration of all instruments, a
stellar cluster for checking geometric distortion in the cameras,
and a planetary nebula for checking the wavelength calibration of
the spectrometer. This sequence was designed such that it could
be rerun, with few if any changes, after completion of the EPOCh
observations and then again just before and just after the
observing program for comet 103P/Hartley 2.
HRII Dark Retake for Lunar Cal
------------------------------
Due to a minor error in the lunar calibration sequence that was
executed in December, a series of HRII dark frames was not recorded.
However that sequence was successfully rerun on 16-17 January 2008.
EPOCh
-----
Start Time : 2008-01-22 (DOY 022)
Stop Time : 2008-08-31 (DOY 244)
EPOCh observations of eight known extrasolar planetary systems
transits began on 22 January 2008 with the HAT-P-4 system and ended
nearly six months later with the HAT-P-7 system on 31 August 2008.
Taking advantage of the permanent on-orbit defocus of the HRI
telescope, EPOCh used the HRIV CCD to collect over 172,000 usable,
photometric-quality, visible light images of eight known transiting
planet systems. Time series of continuous 50-second integrations in a
subframe mode of 128x128 or 256x256 pixels with the clear #6 optical
filter extending from 350 to 1000 nanometers were used to observe each
system for about three weeks, typically covering five or more transits
as well as secondary eclipses. An exception is XO-3 which was
observed only briefly before the spacecraft unexpectedly entered safe
mode. In most instances, the 128x128-pixel subarray size was used.
The 256x256-pixel subarray was utilized during some transit and
secondary eclipse periods to ensure that pointing jitter did not cause
the star to fall beyond the edges of the subarray. Each series was
typically bracketed by a set of dark and internal stimulator lamp
frames to monitor changes in the HRIV CCD detector for calibration
purposes.
The transiting planet systems were observed in the integrated light of
the planet and star; no spatially resolved image of the planet was
possible. The out-of-focus HRI telescope defocuses the images to
about 10 pixels or 4 arcseconds at full-width half-max and introduces
visible structure.
The following extrasolar planetary systems were the targets for EPOCh
transit photometry and are described in Ballard, et al. (2009)
[BALLARDETAL2009]:
Stellar #Transits
Target V_mag Observed Points of Interest
------- ----- --------- -------------------------------------------
HAT-P-4 11.22 10 Low density planet, large radius for
its mass
XO-3 9.91 1 Eccentric orbit, second planet suspected
TrES-3 12.40 7 Short period (31 hours), reflected light
target
XO-2 11.18 3 Fainter component in wide visual binary,
metal rich
GJ 436 10.67 8 Eccentric orbit, unseen planet suspected,
star is M-dwarf
TrES-2 11.41 7 Kepler target, additional planets possible
WASP-3 10.64 8 Strongly heated, reflected light and
visible thermal emission possible
HAT-P-7 10.50 8 Kepler target, even more strongly heated
than WASP-3
On 18-19 March, 28-29 May, and 4-5 June 2008, EPOCh also observed
Earth with the HRIV CCD and the High Resolution Infrared Imaging
Spectrometer (HRII) to characterize it as an analog for extrasolar
planets. The observations comprised imaging in seven optical
narrow-band (100 nanometer) filters and 2- to 5-micron infrared
spectroscopy over a full Earth rotation. Because the HRI telescope
is defocused, the spatial resolution as observed is about 4 arcsec in
each case.
The optical images of Earth used a 512x512-pixel subarray of the HRIV
CCD detector at a scale of about 0.4 arcsec/pixel, and each frame of
the HRII spectrometer was 512 (wavelength) by 128 pixels (spatial,
2-arcsec/pixel scale). HRIV CCD images were acquired once every hour
with three filters centered on 350, 750 and 950 nanometers and once
every 15 minutes with the 450-, 550-, 650- and 850-nanometer filters.
Infrared spectra were obtained twice per hour by scanning the slit
of the HRII spectrometer over the earth, using three scans to ensure
coverage of the entire disk; the slit was aligned perpendicular to
the terminator during the scans. The spacecraft orbit was
approximately in the plane of the ecliptic which provided an
equatorial view of Earth with about 62 to 77 percent of the disk
illuminated. Each of the three Earth observing periods lasted
approximately 24 hours. During the 29 May observation, the Moon
transited Earth as seen from the spacecraft (0.3 AU from Earth).
The following table chronologically lists EPOCh observations. For
most stellar exoplanet transit targets, preview imaging was performed
to determine if the pointing bias needed to be modified for that
target series. Scheduled Earth observations #2 and #3 were canceled
due to a telecommunications anomaly (see below).
Target Start Date/DOY Stop Date/DOY Comments
------- -------------- -------------- --------------------------
HAT-P-4 2008-01-22/022 2008-02-12/043
XO-3 2008-02-12/043 2008-02-17/048 S/C entered safe mode
TrES-3 2008-03-06/066 2008-03-08/068
XO-2 2008-03-09/069 2008-03-11/071 Preview for pointing bias
TrES-3 2008-03-11/071 2008-03-18/078
Earth 2008-03-18/078 2008-03-19/079 Obs #1
XO-2 2008-03-20/080 2008-03-28/088
GJ 436 2008-05-04/125 2008-05-27/148
Earth 2008-05-28/149 2008-05-29/150 Obs #4
Earth 2008-06-04/156 2008-06-05/157 Obs #5
TrES-2 2008-06-28/180 2008-06-29/181 Preview for pointing bias
HAT-P-4 2008-06-29/181 2008-07-08/190
TrES-2 2008-07-08/190 2008-07-17/199
WASP-3 2008-07-17/199 2008-07-19/201 Preview for pointing bias
TrES-2 2008-07-20/202 2008-07-30/212
WASP-3 2008-07-30/212 2008-08-08/221
HAT-P-7 2008-08-08/221 2008-08-10/223 Preview for pointing bias
WASP-3 2008-08-10/223 2008-08-16/229
HAT-P-7 2008-08-16/229 2008-08-31/244
After the observations of XO-3 on 17 February 2008 were downlinked,
the spacecraft autonomously entered safe mode as it was turning to
an optimal attitude to transmit data to Earth. EPOXI mission
controllers believed the safe mode was triggered when one of the
reaction wheels, which helps maintain spacecraft attitude,
experienced slightly higher temperatures than what the on-board fault
protection software would allow. After some engineering data was
slowly brought down to Earth, controllers determined the
spacecraft could be brought out of safe mode without triggering new
problems. On 29 February the spacecraft successfully exited safe
mode and began downlinking the EPOCh images taken before safe mode
was entered.
On 6 March 2008, EPOCh observations were restarted with TrES-3 as
the target. EPOCh imaging continued without problems until a
telecommunication anomaly occurred after the March 28th downlink of
5000 photometric HRIV frames of transiting planet system XO-2. This
was the largest volume of data in a single downlink for EPOXI to
date. Following this downlink, EPOCh observations were paused to
investigate the cause of an 8-dB (33%) loss of downlink signal and
some slightly elevated temperatures on the spacecraft as it passed
through perihelion. As the spacecraft cooled over three weeks (a
combination of moving further from the sun and all instruments being
turned off), telemetry strength returned, and the project restarted
EPOCh by first downlinking the images of XO-2 that had been stored on
board the spacecraft since the end of March. Telecommunications
functioned as expected and observations of stellar exoplanet transit
targets resumed with the remaining scheduled target, GJ 436. The
fourth and fifth sets of Earth observations were performed in late
May and early June as planned, and a standard cruise calibration for
the three instruments was successfully performed on 23-25 June 2008.
During the telecom anomaly, observations of these scheduled targets
were missed: the end of the XO-2 sequence, TrES-2, the second and
third sets of Earth observations, and the beginning of GJ 436. As a
result of skipping these targets, the EPOCh investigation could no
longer meet some of its objectives. Therefore NASA approved
contingency observations starting on 27 June 2008 and continuing
through 31 August 2008 to replace the science lost during the safe
mode entry and telecom problems experienced in the spring. The
targets for the contingent observations were TrES-2, HAT-P-4
(revisit), WASP-3, and HAT-P-7.
While waiting for the EPOCh contingency observations to begin, a
standard cruise calibration was performed on 23-25 June 2008 for the
HRII and HRIV instruments. The sequence was very similar to that
used for the calibration performed on 9 January 2008, except the MRI
instrument was turned off because of thermal and telecommunication
concerns. Also a trajectory correction maneuver was performed to
put the flyby spacecraft on course for a rendezvous with Hartley 2
on 4 November 2010.
Since the second and third sets of EPOCh Earth imaging were canceled
because of the telecommunications anomaly, NASA approved a request
from the team to perform two Earth observations in 2009.
Cruise 2
--------
Start Time : 2008-09-01 (DOY 245)
Stop Time : 2010-09-02 (DOY 245)
Various calibration sequences and tests as well as several Earth
flybys were performed for this phase. During Cruise 2, EPOCh continued
observing Earth as as a contingency for the two observing periods that
were lost in early 2008 because the telecommunications anomaly. EPOCh
also observed Mars as an extrasolar planetary analog and an exoplanet
microlensing event named MOA-2009-BLG-266.
HRII Reciprocity Test
-------------------
On 18 September 2008, an HRII reciprocity test was performed to
determine the background signal level of the READ and RESET frames
of the IR spectrometer as a function of the past history of
integration delay times and the timing gap between sets of frames
using the diagnostic imaging mode (number 6). The ultimate
objective of this test along with the HRII Dark Flush, HRII Dark
Gap, and HRII Subframe Gain tests performed over the next four
months is to develop a more accurate model of the variation in the
background level of the IR spectrometer.
HRII Dark Flush Test
--------------------
On 26 September 2008, an HRII dark frame flush test was performed
to determine the type of IR spectrometer instrument operation
needed to remove all traces of the residual (previous) image.
HRII Encounter Darks Rerun
--------------------------
On 02 October 2008, a set of HRII dark frames for several IR
exposure IDs from the Deep Impact Tempel 1 encounter sequence was
acquired by the HRII spectrometer. The exposures were those
acquired from about 19 minutes before the impact with Tempel 1
through the first few hours of lookback imaging.
HRII Dark Gap Test
------------------
On 10 October 2008, an HRII dark gap test was performed to
characterize the change in the residual image and the dark level
in the IR spectrometer as a function of wait time and number of
readouts after acquiring data in the subframe imaging modes
(numbers 2 and 3).
First Interplanetary Internet Test
----------------------------------
From mid-October to mid-November 2008, the first deep space
communications network, also known as the Interplanetary Internet,
was successfully tested using the Deep Impact flyby spacecraft.
Using software called Delay-Tolerant Networking (DTN) dozens of
images were transmitted to and from the flyby spacecraft located
more than 32 million kilometers from Earth.
HRIV PSF Calibration
--------------------
On 17 December 2008, additional data were acquired for improving
point spread functions (PSF) for the HRIV CCD. Analysis of early
EPOXI calibration data and EPOCh stellar observations indicated
the PSFs had changed since mid-2005 when the functions were last
generated for Deep Impact. The project plans to rerun this
sequence in 2010 for the Hartley 2 flyby.
Earth Flyby #2
--------------
At about 21:40 UTC on 29 December 2008, the Deep Impact flyby
spacecraft achieved its closest approach to Earth at an altitude
of only about 43,450 km, about midway between New Zealand and
Tierra Del Fuego and at a latitude of about 49 degrees south.
HRII Subframe Gain Calibration
------------------------------
On 26 January 2009, an HRII subframe gain calibration was
conducted to observe differences in the IR spectrometer signal
response rates when observing an external radiance source to
differentiate between gain and offset effects when using the
various subframe modes. The test was performed by scanning the
spectrometer across the moon at multiple speeds with various
subframe modes while the HRI telescope barrel was warm.
EPOCh Earth North Pole
----------------------
On 27-28 March 2009, EPOCh observed Earth at high northern latitudes
for 24 hours with the HRIV CCD and the IR spectrometer to continue
characterizing it as an analog for extrasolar planets. The
observations comprised narrow band filter images (350-950
nanometers) and 2- to 5-micron infrared spectroscopy, over a full
Earth rotation. Observations were acquired once per hour with the
filters centered on 350, 750 and 950 nanometers, whereas the 450-,
550-, 650-, and 850-nanometer data were taken every 15 minutes.
Infrared spectral scans of the Earth's disk were acquired twice per
hour.
HRII Lunar Radiometry & Flats
-----------------------------
On 1-2 June 2009, the HRII spectrometer acquired a series of
north/south scans of the moon for lunar radiometry and east/west
scans along IR slit for flats. These data were the best obtained
to date for the purpose of generating flat fields for the IR
spectrometer.
HRII Lunar Radiometry & Anti-saturation Filter
---------------------------------------------
On 9 June 2009, the HRII spectrometer imaged the moon using
north/south scans to better characterize the effects of the
anti-saturation filter in the IR spectra.
HRII Linearity Calibration
--------------------------
On 18 June 2009, HRII darks were acquired to check the linearity
of the IR spectrometer. The sequence was identical to the one
used during standard cruise calibrations for linearity.
Distant Earth Flyby #1
----------------------
A distant flyby of Earth occurred on 29 June 2009 at a geocentric
distance of about 1,350,000 km.
EPOCh Earth South Pole #1 (partial)
-----------------------------------
On 27-28 September 2009, EPOCh observed Earth at high southern
latitudes with the HRIV CCD and the IR spectrometer using the same
sequence as the observations at northern latitudes in March 2009
to continue characterizing it as an analog for extrasolar planets.
However the sequence ended prematurely because HRI was turned off
by fault protection although the spacecraft was fine. MRI remained
on.
Checkout after HRI Turnoff & HRIV Mechanical Checkout
-----------------------------------------------------
Before repeating the Earth South Pole observation, a standard
imaging checkout of the HRII, HRIV, and MRI instruments was
performed after HRI was powered up on 30 September 2009. Also
a mechanical checkout of HRIV was performed on 01 October:
a miniature HRIV Earth observing sequence that cycled through
the filters 21 times was run to check for 5-V telemetry channel
noise. The results of the tests were satisfactory.
EPOCh Earth South Pole #2 (Full)
--------------------------------
On 04-05 October 2009, EPOCh successfully acquired a full set of
observations (24 hours) of Earth with the HRIV CCD and the IR
spectrometer using the same sequence as the observations at high
northern latitudes in March 2009 to continue characterizing it as an
analog for extrasolar planets. The observations comprised narrow
band filter images (350-950 nanometers) and 2- to 5-micron infrared
spectroscopy, over a full Earth rotation. Observations were acquired
once per hour with the filters centered on 350, 750 and 950
nanometers, whereas the 450-, 550-, 650-, and 850-nanometer data
were taken every 15 minutes. Infrared spectral scans of the Earth's
disk were acquired twice per hour.
EPOCh Microlensing MOA-2009-BLG-266
-----------------------------------
On 05-08 October 2009, HRIV imaged about four days the known
exoplanet microlensing event named MOA-2009-BLG-266, where the
foreground lensing star and its exoplanet bend light of the source
star. EPOCh reused the sequence from the HRIV exoplanet transit
observations in 2008 to obtain these data. A second campaign to
observe MOA-2009-BLG-266 in early 2010 for parallax measurements
was canceled in preparation for the Hartley 2 encounter.
HRII Radiometric Cal #1 (Beta Hyi)
----------------------------------
From 13 October to 24 October 2009, the HRII spectrometer imaged
the star Beta Hyi to improve the radiometric calibration for that
instrument.
HRII Dark Subframe Test
-----------------------
On 20 November 2009, the HRII spectrometer acquired dark frames
to further characterize the response for the subframe imaging modes
(numbers 2 and 3).
EPOCh Mars Obs
--------------
On 20-21 November 2009, EPOCh observed Mars for 24 hours with the
HRIV CCD and the IR spectrometer, reusing the Earth sequence, to
characterize it as an analog for extrasolar planets and look for
methane. The observations comprised narrow band filter images
(350-950 nanometers) and 2- to 5-micron infrared spectroscopy, over
nearly a full Mars rotation. Observations were acquired once per
hour with the filters centered on 350, 750 and 950 nanometers,
whereas the 450-, 550-, 650-, and 850-nanometer data were taken
every 15 minutes. Infrared spectral scans of Mars' disk were
acquired twice per hour.
HRII Lunar Flats/Radiometric Cal #1 and
HRII Lunar Flats/Radiometric Cal #2
-----------------------------------
On 05 and 12 December 2009 as the spacecraft approached Earth, the IR
spectrometer made north/south scans of the moon for radiometry and
east/west scans along the slit for lunar flats and a radiometric
calibration.
HRII Lunar South Pole Radiometry
--------------------------------
On 18 December 2009, about 10 days before the distant flyby of Earth
the IR spectrometer made north/south scans of the lunar south pole
for radiometric analysis.
Distant Earth Flyby #2
------------------------------
Another distant flyby of Earth occurred 28 December 2009 at a
geocentric distance of about 1,330,000 km.
Standard Cruise Calibration
---------------------------
A full, standard cruise calibration for HRII, HRIV, and MRI was
completed on 16 February 2010.
HRII NoSave Flush Test
----------------------
On 20 April 2010, tested an HRII sequence designed to reduce the
amount of charge buildup that results in abnormally high signals in
the first 1 to 4 images of a multi-frame IR exposure. The sequence
consisted of flushing the IR detector before science imaging by
alternating between saving frames of one exposure ID for science
and not saving those from the next exposure (i.e., flush frames).
HRII Radiometric Cal #2 (Beta Hyi)
----------------------------------
From 03 May to 17 May 2010, the HRII spectrometer imaged the star
Beta Hyi to further improve the radiometric calibration for that
instrument.
Earth Flyby #3
--------------
The final near flyby of Earth for the EPOXI mission occurred on 27 Jun
2010 at a geocentric distance of about 30,426 km.
MRI Dosido Fast Slew Test
--------------------------
On 12 July 2010, the MRI Dosido fast slew sequence involved a
test of the observing strategy planned from 8 days to one day
before the Hartley 2 encounter that included periods during which
the spacecraft attitude was maneuvered once per hour between the
Earth downlink attitude and the comet viewing attitude. The
spacecraft was slewed at a high rate between these two attitudes,
and the Deep Space Network was required to lockup on the downlink
quickly every hour. MRI images of dark space were taken each hour
at the comet viewing attitude as they will be during the actual
encounter sequence in early November 2010.
DIXI/Hartley 2
--------------
Start Time : 2010-09-03 (DOY 246)
Stop Time : 2010-11-28 (DOY 332)
HRIV PSF Calibration
--------------------
On 03 September 2010, the HRIV CCD imaged Canopus to monitor the
point spread functions (PSF) for that instrument. Analysis of HRIV
calibration data since 2005 and EPOCh stellar observations in 2008
indicate the PSFs can change over time.
Approach Imaging: E-60 to E-50 Days (VIS only)
----------------------------------------------
The MRI and HRIV visible instruments began imaging 103P/Hartley 2
every six hours on 05 September 2010, 60 days before the encounter
(E-60 days) encounter and continued for 10 days. However due to
thermal issues with a traveling wave tube amplifier the entire HRI
system including the HRIV CCD was turned off on 06 September until
20 September. MRI continued its imaging sequence as planned through
E-50 days. The comet was observed for 16 hours at a time with 8
hours devoted to downlinking the data.
Approach Imaging: E-50 to E-40 Days (VIS only)
----------------------------------------------
From 15 to 25 September 2010, the imaging cadence for MRI increased
to every two hours. On 20 September the HRIV CCD was turned on, and
it begin imaging 103P/Hartley 2 once every two hours for the
duration of the period. The comet was observed for 16 hours at
a time with 8 hours devoted to downlinking the data.
Pre-Encounter Standard Cruise Calibration
-----------------------------------------
A full, standard cruise calibration for HRII, HRIV, and MRI was
performed on 28-29 September 2010.
Approach Imaging: E-34 to E-8 Days (Start HRII)
-----------------------------------------------
From 01 to 28 October 2010, MRI and HRIV imaged 103P/Hartley 2 about
every 5 minutes while the HRII spectrometer scanned for outbursts
once every 30 minutes. The instruments observed the comet for 16
hours per day allowing for 8 hours of downlinking; the same sequence
was repeated daily yielding one full cycle per day. Data from the
6th cycle on 06 October 2010 (DOY 279) were never downlinked because
of a pointing problem with the Deep Space Network. Those data had
to be erased on board the spacecraft to make room for the next daily
cycle and could not be recovered.
Approach Imaging: E-8 Days to E-18 Hours
----------------------------------------
From 28 October to 03 November 2010, the MRI and HRIV imaged
103P/Hartley 2 continuously and HRII scanned the comet about every
hour for 16 hours per day allowing for 8 hours of downlinking
punctuated by hourly maneuvers, called dosido, to observe the comet.
During this imaging phase there was only a single downlink of all
images with zero margin; thus some images were occasionally lost as
expected. The first cycle (DOY 300/301) was abbreviated such that
the first comet-imaging session was only 6-hours long, followed by
the standard 8-hour dosido.
Encounter Imaging: E-18 Hours to E+2 Days
------------------------------------------
From 03 to 06 November 2010, the HRII, HRIV, and MRI performed high
resolution encounter imaging of 103P/Hartley2. The HRIV and MRI
instruments began sampling about once every two hours until one
hour before encounter when the cadence changed to once every 15
minutes. At E-30 minutes the instruments began continuously
imaging of the comet. At E+30 minutes simultaneous observing and
data playback began with samples being taken every 30 minutes.
During the encounter imaging period, HRII infrared scans occurred
every two hours until four hours prior to encounter when the
cadence increased to hourly then more frequently one hour before
closest approach. About one hour after closest approach, regular
infrared sampling at 30-minute intervals resumed.
Departure Imaging: E+2 to E+12 Days
-----------------------------------
From 06 to 16 November 2010, the HRII spectrometer scanned
103P/Hartley 2 every 15 minutes while the MRI CCD imaged the
comet every 2 minutes and HRIV once every hour.
Departure Imaging: E+12 to E+21 Days
------------------------------------
From 16 to 26 November 2010, the HRII spectrometer scanned
103P/Hartley 2 every 30 minutes, and HRIV performed rotation
sampling at the same cadence. MRI performed rotation sampling
every 30 minutes and imaging using gas filters every two to four
hours.
Post-Encounter Standard Cruise Calibration
-----------------------------------------
A full post-encounter standard cruise calibration for HRII, HRIV,
and MRI was performed on 27-28 November 2010. The sequence was
nearly identical to the pre-encounter calibration performed in
September.
Cruise 3
--------
Start Time : 2010-11-29 (DOY 333)
Stop Time : 2011-02-06 (DOY 037)
HRII 50-Frame Extended Linearity Calibration
--------------------------------------------
From 05 to 06 February 2011, the HRII spectrometer took 50 dark
frames for a set of integration times and for each imaging mode
to gather enough data to perform a thorough analysis of the
linearity of each active pixel in the IR focal plane array.
Recommended Reading
===================
Relevant Publications from Deep Impact
--------------------------------------
Information about the design of the Deep Impact mission, scientific
objectives, and instrumentation that are relevant to EPOXI are found
in the work by A'Hearn, et al. (2005) [AHEARNETAL2005B], Blume
(2005) [BLUME2005], Hampton, et al. (2005) [HAMPTONETAL2005],
Klaasen, et al. (2005), Mastrodemos, et al. (2005)
[MASTRODEMOSETAL2005], Thomas, et. al. (2005) [THOMASETAL2005], and
Yeomans, et al. (2005) [YEOMANSETAL2005]. The calibration of the
Deep Impact instruments and the resulting data processing pipeline
are explained by Klaasen, et al. (2008) [KLAASENETAL2006] and
Klaasen, et al. (2005) [KLAASENETAL2005]. Image restoration to
correct for the HRI defocus is described by Lindler, et. al (2007)
[LINDLERETAL2007].
Initial results from the encounter at comet 9P/Tempel 1 in July 2005
are described by A'Hearn, et al. (2005) [AHEARNETAL2005A]. A
summary of the results from Deep Impact are presented by A'Hearn and
Combi, (2007) [AHEARN&COMBI2007], A'Hearn and Combi, (2007)
[AHEARN&COMBI2007B], and A'Hearn and Combi, (2007)
[AHEARN&COMBI2007D]. Three volumes of Icarus are dedicated to
results from Deep Impact. Please see Combi and A'Hearn, (2007)
[COMBI&AHEARN2007], Combi and A'Hearn, (2007) [COMBI&AHEARN2007B],
and A'Hearn and Combi, (2007) [AHEARN&COMBI2007C]. Belton, et al.
(2011) [BELTONETAL2011] discuss how the central horizontal gap of
the VIS CCDs was handled for aperture photometry of 9P/Tempel 1.
EPOXI
-----
For a brief overview of the EPOXI mission including the EPOCh and
DIXI investigation, see A'Hearn (2008) [AHEARN2008], A'Hearn, et al.,
(2008) [AHEARNETAL2008], Deming, et al., (2007) [DEMINGETAL2007],
Deming, et al., (2008) [DEMINGETAL2008], and Deming, et al., (2008b)
[DEMINGETAL2008B].
Initial results from the EPOCh investigation are presented by
Ballard, et al., (2008b) [BALLARDETAL2008B], Ballard, et al., (2009)
[BALLARDETAL2009], Christiansen, et al., (2008)
[CHRISTIANSENETAL2008], and Hewagama, et al. (2008)
[HEWAGAMAETAL2008].
Detailed results based on the EPOCh observations of transiting planet
systems are presented in conference proceedings by Christiansen, et
al., (2009) [CHRISTIANSENETAL2009], Ballard, et al., (2009b)
[BALLARDETAL2009B], and Ballard, et al., (2010) [BALLARDETAL2010B] as
well as in publications by Ballard, et al., (2010) [BALLARDETAL2010],
Christiansen, et al., (2010) [CHRISTIANSENETAL2010], Christiansen, et
al., (2011) [CHRISTIANSEETAL2010B], and Ballard, et al., (2011)
[BALLARDETAL2011].
Detailed results based on the EPOCh Earth observations are presented
in publications by Cowen, et al., (2009) [COWANETAL2009] and
Livengood, et al., (2009) [LIVENGOODETAL2009] and in conference
proceedings by Robinson, et al. (2009) [ROBINSONETAL2009].
Rieber and Sharrow, (2009) [RIEBER&SHARROW2009] discuss the design
approach for EPOCh exoplanet transit imaging as well as the pointing
stability of the flyby spacecraft.
Initial results from the DIXI investigation are presented in
A'Hearn, et al., (2011) [AHEARNETAL2011]. Sunshine, et al., (2009)
discuss the variability of OH/H2O on the lunar surface based on
HRII calibration data [SUNSHINEETAL2009]. Klassen, et al, (2011)
[KLAASENETAL2011] describe the changes implemented to the EPOXI
pipeline for processing Hartley 2 data.
Mission Data
============
The following mission-related data are or will be archived at the PDS:
o Raw HRII, HRIV, and MRI science and calibration observations
acquired throughout the mission,
o Calibrated EPOCh exoplanet transit observations, including
exoplanet microlensing event MOA-2009-BLG-266, in units of
radiance (HRIV only),
o Calibrated EPOCH Earth observations in units of radiance (HRII
and HRIV) and I/F (HRIV),
o Calibrated EPOCH Mars observations in units of radiance (HRII
and HRIV) and I/F (HRIV),
o Raw and calibrated science observations acquired during the
approach to and encounter with comet Hartley 2 (HRII, HRIV,
and MRI),
o Raw and calibrated navigation images acquired during the
approach to comet Hartley 2 (HRIV and MRI),
o Radio science data from the Hartley 2 encounter,
o SPICE data, including 5-Hz telemetry from the Attitude
Determination and Control System (ADCS) as a CK kernel,
o Higher-level products, including light curves for EPOCh stellar
transit (exoplanet) targets, EPOCh color maps of Earth, and a
shape model and surface temperature maps for Hartley 2, and
o Select data from the Earth-based observing campaign for the
Hartley 2 encounter.
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