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February 2005
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Mission - Mission Update

Mission Update - February 2005

What is the team doing during the first days after launch of a spacecraft? From the time Deep Impact launched, it entered a phase called commissioning of the spacecraft. During that time, the team verifies the basic state of health of all of the subsystems and confirms that all the instruments are operating and calibrating properly. For Deep Impact, this phase will run for about 40 days. Take a look at some of the early daily logs on commissioning from Mission Manager, Dave Spencer. Then learn more about Dave Spencer.

DI Mission Log (excerpts)
Dave Spencer, Mission Manager

January 16, 2005
Following downlink of logs, the instrument turn-on sequence was activated and the medium resolution imager on the flyby spacecraft (MRI) powered on as expected. The activity lead provided the following summary: "The flyby lunar science calibration sequence executed beautifully. The calibration consisted of four major slews (a movement of the telescope) and several smaller slews and infrared (IR) scans for a total of forty slews. The major slews were: (a) cruise attitude to the Moon (1300 s duration), (b) the Moon to the Earth (600 s duration), (c) the Earth to the calibration reference star, iCar (2400 s duration), and (d) the return slew from iCar to cruise attitude (1600 s duration).

All slews completed as expected. Preliminary analysis indicates that both the high resolution imager on the flyby spacecraft (HRI) and MRI performed as expected, with no errors. All expected HRI visible (54 total), HRI IR (185 total), and MRI visible images (52 total) have been confirmed in non-volatile memory via directory listings of the A:/a and C:/c drives on Spacecraft Computer Unit-A."

January 17, 2005
The high gain antenna (HGA) was unlocked from its stowed position. Gimbal checkouts were performed, and full-range of motion testing of both the Y- and Z-gimbals were performed. Downlink was switched from the Low Gain Antenna (LGA) to the HGA, and the Deep Space Network (DSN) locked up successfully on HGA downlink telemetry at 2 kbps and 200 kbps.

All image files collected during the lunar science calibration were downlinked once again. With the higher signal-to-noise ratio provided by the HGA, there were very few corrupted downlinks. The HRI bakeout heaters were turned on.

January 18, 2005
The FSW (Flight Software version 6.2.4) activity (upload to spacecraft) was reviewed, and approved for execution tomorrow.

January 19, 2005
Flight software tests were performed on both flight computers. Both computers are healthy.

Deep Impact entered safe mode tonight at DOY 020/0700 UTC following loss of star tracker lock and buildup of attitude errors. The spacecraft attitude error fault response was initiated, putting us on thrusters and going to sun acquire (Y-axis pointed at the sun). An X7-class solar flare is believed to be the cause. See the plot below for the sun's x-ray flux (vertical axis) versus time (horizontal axis).

GOES X-Ray Flux (5 minute data)
(Click to enlarge)

Safing recovery continues in the morning when we have a full crew.

January 20, 2005
At this morning's meeting, ADCS presented the sequence of events leading to our safe mode entry last night. The safing event was precipitated by an X7 category solar flare, effectively blinding our star trackers. The spacecraft was in a safe and stable state.

The flight team spent today developing and beginning the implementation of our safe mode recovery plan. If the space weather cooperates, safe mode recovery could be completed as early as tomorrow.

January 21, 2005
Commands were sent to slew the spacecraft to its nominal cruise attitude, placing the solar array normal 23 deg off-Sun. The high gain antenna was activated, and the communications link was transitioned from the LGA (low gain antenna) to the HGA (high gain antenna) at a 200 kbps downlink data rate. Stored telemetry was downlinked. Safe mode recovery was complete by DOY022/0406 UTC.

January 22, 2005
Commands for the MRI stray light test, scheduled for Monday, January 24, were reviewed and approved. Stored telemetry was downlinked. Solar flux measurements from the GOES satellite have returned to benign levels.

February 11, 2005
Deep Impact successfully performed TCM-1 today. The burn magnitude of 28.57 m/s was achieved per the design. Initial navigation estimates indicate that the maneuver execution errors were well within 1%.

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