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EPOXI

Two intriguing investigations -- One flight-proven spacecraft

Mission Status Reports

Mission Status Reports

DATE
WHO		 REPORT
04.28.2008
A'Hearn		 Cooling Down
The spacecraft's signal strength has returned to expected performance after losing about 8dB during perihelion (closest point to the sun). At the end of last week, as the spacecraft cooled (a combination of moving further from the sun and all instruments being turned off), telemetry strength returned. Observations for EPOCh are scheduled to be resumed at the end of this week.
04.02.2008
Deming		 EPOCh Observes X0-2
On March 28, EPOCh downlinked over 5000 photometric CCD frames of the metal-rich transiting planet system XO-2. The was the largest volume of data in a single downlink for EPOXI to date. Following this downlink, EPOCh observations have been paused, to investigate the cause of a weaker-than-normal downlink signal, and some slightly elevated temperatures on the spacecraft.
03.26.2008
Deming		 EPOCh Observes TrES-3
EPOCh has recently completed observations of the massive hot Jupiter exoplanet, TrES-3 (pronounced "trace three"). After recovering from safe mode on March 6, EPOXI promptly observed 5 transits, and 6 secondary eclipses of TrES-3. On March 18, EPOXI observed the Earth for a full 24-hour rotational cycle, obtaining narrow-band visible images and infrared (1.5-4.5 micron) spectroscopy. The EPOCh science team will use the Earth data to define the properties of the "Earth-as-an-exoplanet", i.e. the rotational light curve of Earth's integrated light. This light curve should exhibit signatures due to cloud patterns and vegetation on the land masses, and similar signatures may eventually be observable for Earth-like exoplanets. On March 20, EPOXI turned to observe transits of the metal-rich giant planet system XO-2.
03.03.2008
Duxbury		 Back to Normal Ops
EPOXI exited safemode Friday (29 Feb) and is currently downlinking the EPOCh images taken before safemode entry. New EPOCh imaging will begin on Thursday (6 Mar). EPOXI is now back to normal operations.
02.25.2008
A'Hearn		 Safe Mode Update
The Deep Impact spacecraft continues to be in "safe mode" with that mode's very slow communication links to Earth. Although the hiatus interrupted EPOCh observations, the scientific output will not be compromised because additional observations can be carried out after the previously scheduled end of operations for EPOCh. Therefore, there has been no rush to bring the spacecraft out of safe mode, since the spacecraft is healthy and safe in that mode. Enough of the engineering data has now been brought down to Earth to give us confidence that we can bring the spacecraft out of safe mode without triggering new problems. Assuming that all goes as planned we anticipate resuming observations for EPOCh next week, beginning with downlinking the several days' worth of data that were stored on board prior to entering safe mode.
02.19.2008
Duxbury		 Spacecraft in Safe Mode
NASA's Deep Impact spacecraft has temporarily halted EPOCh (Extrasolar Planet Observation and Characterization) observations starting this past Sunday, Feb. 17. The pause was generated when the spacecraft entered safe mode - a condition where all but essential systems are turned off until the spacecraft receives new commands from mission control.
Safe mode was entered while the spacecraft was turning to an optimal attitude to transmit data to Earth. The spacecraft is currently communicating with Earth, and EPOXI mission controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif. anticipate no major challenges to returning the spacecraft to the planned EPOCh observations. They believe 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.
02.04.2008
Deming		 EPOCh Observes HAT-P-4
EPOCh observations of the giant transiting planet HAT-P-4 began on January 22. The initial observations showed a pointing discrepancy that caused the star to move out of our field of view about 20% of the time. The EPOCh team was able to make some technical adjustments to the spacecraft that improved the pointing, thanks to the collaborative efforts of the flight team at JPL, the spacecraft engineers at Ball Aerospace, and the EPOCh science team. These efforts have led (as of Feb 2) to the successful collection of tens of thousands of observations of HAT-P-4, and the EPOCh science team has confirmed that the giant planet transits are seen in these data. Ongoing efforts to improve the calibration of the data will allow sensitivity to small planets that we hope to discover in our target systems.
01.21.2008
A'Hearn		 PI miscellaneous thoughts
On 9 January we carried out the first of our standard cruise calibrations. These observations include observations of several standard stars, both solar analogs and hot stars with few absorption lines in their spectra, both for absolute calibration of all instruments, a cluster for checking geometric distortion in the cameras, and a planetary nebula (NGC 7027) for checking the wavelength calibration of the spectrometer. This sequence, with few if any changes, will be rerun after completion of the EPOCh observations and then again just before and just after the observing program for comet Hartley 2.
Due to a minor error in the lunar calibration sequence, a series of IR dark frames was not recorded but that sequence was rerun on 16 Jan and all data are now at the science data center.
12.31.2007
A'Hearn		 Lunar Calibration and Flyby
Today, 31 December, the Deep Impact flyby spacecraft, executed its flyby of Earth to set it on course for its EPOXI activities - observations of extrasolar planets for EPOCh and an encounter with comet Hartley 2 for DIXI. The encounter went just as expected. Analysis of tracking data over the next week or two will allow us to determine how accurately we are on track and whether a "cleanup" maneuver is needed just before we begin the EPOCh observations. Since launch, the spacecraft has executed maneuvers flawlessly and we have skipped many of our scheduled "cleanup" maneuvers, including skipping the one in late November to take out errors in the maneuver of 1 Nov.

Two days ago, 29 December, we took numerous observations of the moon to calibrate our scientific instruments. The most crucial of these calibrations was a set of sweeps across the moon with the spectrometer in order to determine the "flat field" characteristics of the IR detector in the spectrometer. This is needed to carefully remove the pixel-to-pixel variations in the response of the instrument. We were unable to do this effectively on the prime mission because we passed the moon so soon after launch and this particular piece of the calibration requires a large, bright source. All of the data have been received on the ground and we are beginning our analysis of the calibration data. The spacecraft did everything we asked it to do and in general the data look very good. It will be several weeks to a couple of months before we have all these data folded into our calibration pipeline for processing the data of more direct scientific interest.
12.17.2007
A'Hearn		 Scattered Light Calibration
Today, 17 December, EPOXI carried out a calibration for scattered light using Earth's moon. The spacecraft is on course to get a gravity assist from Earth on 31 December and to do a primary calibration on the moon on 29 December. Many of today's 66 images were obtained with the moon outside but near the field of view of the cameras. The images were brought to the ground via the DSN to JPL and then sent to the Science Data Center. They are now available to the science team for analyzing the amount of light that is scattered into the field of view from bright objects just outside or within the field of view.
12.03.2007
A'Hearn		 EPOCh has data!
The EPOCh team is excited to learn that EPOXI is now a fully approved mission, and we congratulate Dr. A'Hearn and the DIXI team on their impressive plans for the Hartley-2 encounter.

On November 5, EPOXI's spacecraft observed a bright (V=9) visual binary star for 12 continuous hours, as a test of pointing and photometric stability. The observations were taken using the 256 x 256 subarray mode of the HRI's CCD. The spacecraft successfully captured the star images and held them on the subarray for the full duration of the test. We were initially puzzled because they appeared to be offset from the central 128 x 128 subarray that we will use for the EPOCh observations. This is 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. We are now examining Deep Impact stellar data taken since the release of the impactor. These data will refine our knowledge of the boresight between the star tracker and the HRI. Factoring in corrections for aberration, we anticipate excellent pointing precision for the EPOCh targets.

Examination of the photometric time series from the test shows that, after applying flat-field calibrations, intensity is correlated with position on the CCD, so the EPOCh photometry team plans to refine the flat-fielding corrections. The photometry is already at the milli-magnitude level of precision, and even greater precision will result from more refined flat-fielding.

The first EPOCh transit observations will occur on January 23, as we target a transit and eclipse of the giant, massive exoplanet HAT-P-2!
12.02.2007
A'Hearn		 Hartley 2 Approved
Following the surprising realization in mid-October that, despite tremendous efforts by many observatories and observers, we could not recover comet Boethin in time to plan our flyby of Earth, we recommended to NASA that we be allowed to fly to our backup target, comet Hartley 2. As indicated in previous messages, NASA allowed us to target the Earth flyby (which will happen on New Year's eve) to go to Hartley 2 and the relevant maneuver was executed on 1 Nov.

Meanwhile, the team assessed the many issues associated with Hartley 2:
- can we confidently deliver as much science as we promised?
- does the spacecraft have enough fuel to get there reliably?
- are there parts that will wear out because of the extra two years in space?
- how much more will it cost just to fly the spacecraft an extra two years?

On Friday, 30 Nov, we presented our plans and assessments to the NASA Science Mission Directorate. They agreed that our science was intact at comet Hartley 2 and that the margin on all mission related engineering was adequate, i.e. that the risks were low. They therefore approved our mission to comet Hartley 2. The EPOCh program of characterizing extra-solar planetary systems will be carried out, as originally planned in the first half of calendar 2008. The spacecraft will then go into hibernation for approximately two years, unless NASA approves another program with separate funding to use the spacecraft during those two years, and will be reawakened in summer 2010 for an encounter with Hartley 2 that is currently planned for 11 October 2010.
11.12.2007
A'Hearn		 EPOXI's First Observations
EPOXI made its first targeted (pointed at a specific target) observations during the past week. The High Resolution Instrument (HRI) was used to take repeated, white-light images of a pair of 9th magnitude stars in the constellation Ursa Major. The observations consisted of more than 1500 30-second exposures and continued for over 12 hours. The data were transmitted from the spacecraft to the ground on Thursday (8 Nov). The purpose of these observations was to test the stability of the instrument because the EPOCh program requires far higher precision in its photometry than was required for Deep Impact. Members of the EPOCh team are now working to study the details of the photometric stability in these data.

Clarification: The photometric test observations for EPOCh were actually obtained on Nov 5. Due to a downlink problem in the first attempt right after the data were taken, they were not downlinked from the spacecraft to JPL's Deep Space Network until Nov 8. They were then transferred from the JPL flight operations computer to the science team's data center early on the morning (EST) of Nov 9.
11.05.2007
A'Hearn		 New Target
In the first half of October, Karen Meech organized an heroic effort to recover comet Boethin in time to plan the spacecraft's flyby of Earth, which would put it on target to go to the comet. The orbit is very uncertain due to the comet having been observed at only two apparitions, with no observations since 1986, and the uncertainty is so large that we would not have enough fuel on board to compensate for the uncertainty in the orbit after the flyby of Earth. This effort was not successful.
As a result, I recommended to NASA that we switch to our backup target, comet 103P/Hartley 2, which has a very well defined orbit but which requires two extra years for the mission and thus additional funding from NASA. The encounter for the backup plan is on 11 October 2010.
NASA authorized us to plan and execute the Earth flyby as though we were going to comet Hartley 2, while they consider whether they can afford to pay for the longer mission. The maneuver to set up the flyby of Earth was executed on 1 November and appears to have been flawless. The flyby of Earth will occur on New Year's Eve, 31 December 2007.
10.04.2007
A'Hearn		 Instrument Check
Today the scientific instruments on the spacecraft were turned on for the first time in more than two years. We confirmed operation of mechanical components (shutters, filter wheels) and detector readouts. The "observations" have been transmitted to Earth and everything seems normal. The images, of a random point in the sky, show stars and both the optical and the infrared detectors show nominal behavior of the background levels and the optical detectors show nominal response to an internal lamp. Detailed analysis over the next few days will determine whether anything has drifted in the two years. Observations of specific targets will start in early November.
09.26.2007
A'Hearn		 DI Wakeup
On Mon-Tue, 24-25 Sept 2007, we woke up the DI flyby spacecraft. During this wakeup we checked only the basic health and safety of the spacecraft and everything seems to be as expected. Since July of 2005, the spacecraft has been awakened roughly once every 6 months to check its health and safety and then put back to sleep. Now we are keeping it awake. We will obtain several days of tracking data to ensure that we know the orbit accurately. The next on-board activity is scheduled for Thur, 4 Oct, when we will turn on the scientific instruments and check out their basic functionality. The instruments have not been turned on since July 2005, but we fully expect them to be as healthy as the spacecraft.