Deep Impact

 2005-001A

---

NASA Discovery class mission which will attempt to hit a comet nucleus in 2005. The Jet Propulsion Lab's Deep Impact probe will be built by Ball Aerospace and consists of a flyby spacecraft and an impactor. Deep Impact will be launched from Cape Canaveral in Dec 2004 and head for comet 9P/Tempel-1. 24 hours before impact, the 350-kg copper impactor spacecraft will separate. The impactor uses autonomous navigation software, pioneered on the Deep Space 1 mission, to control firings of its gas jets and close in for a 10 km/s collision with Tempel-1's nucleus. The 20-meter-deep crater will break through the nuclear mantle and expose the material underneath. The crater and ejecta will be imaged by the flyby probe's camera and infrared spectrometer and by Earthbound astronomers, treated to a spectacular extraterrestrial fireworks display timed for July 4th, 2005. If comets become dormant because their ices are exhausted, the display will soon be over, but if dormancy is due to the mantle locking in the volatile material, Tempel-1 may continue to shine from the hotspot as it loses material from the crater area.

Discovery mission selected 1999 Jul.

Deep Impact has a launch mass of 973 kg (JScR; Delta media kit 976; Ball kit says 1020 kg, NASA kit says 601 kg full, 515 kg dry plus impactor 372 kg full 364 kg dry). and contains a 370 kg copper penetrator which would impact P/Tempel-1 at 10.2 km/s and make a 20-m deep crater to expose raw comet nucleus material. PI is M A'Hearn (U Md). Built by Ball Aerospace. Project management at JPL. Launch Jan 2004 by Delta 7925, encounter 2005 Jul 4.

Shortly before launch it was determined that the originally desired trajectory could not be attained, requiring a significant initial trajectory correction by the spacecraft. In the event the C3 energy was 1.6 sigma low (10.7554 km2/s2 vs 10.8577); achieved asymptote was (199.3849, -2.8416). a TCM-1 of 27.7 m/s was required (in the event,28.6m/s was targeted due to other considerations). The initial intended Tempel-1 B-plane miss was (-60211, 10083) km with TCA at 2005 Jul 4 0622:43 UTC.

After the impact the comet brightened by a factor of 5 within 15 minutes and faded slowly over a few hours.

The flyby spacecraft was reactivated in 2007 for a second comet flyby mission. It was renamed EPOXI (EPOCh and DIXI). The spacecraft will fly by 103P/Hartley 2.

The Deep Impact flyby spacecraft has sufficient fuel to undertake further studies. The new mission, named EPOXI, is comprised of two projects with different scientific objectives. DIXI, the Deep Impact Extended Investigation, continues the original Deep Impact theme of studying comets by flying past comet Hartley 2. A comparison of Hartley 2 with comets observed by other spacecraft missions in order to help determine which cometary features are primordial and which are the result of subsequent evolutionary processes will be a primary focus of the investigation.

EPOCh, Extrasolar Planet Observation and Characterization, will use the Deep Impact high-resolution instrument (HRI) to observe three stars with known transiting giant planets to characterize those planets and to search for others. This is accomplished by using the HRI as a photometer to measure the light coming from the star in frequent images (a typical rate of every 50 seconds) as the planet transits and is later eclipsed by the star. Characteristics of the light from the planet are measured when it is eclipsed by the star, and the presence of other planets may be detected by their transits or by gravitational effects on the position of the giant planet. Planets as small as three Earth masses may be detected in this way. EPOCh will also observe the Earth in visible and infrared wavelengths to allow comparisons with future discoveries of Earth-like planets around other stars.

DI
Date	Time	Event	Orbit
2005 Jan 12	1847:08	Launch by Delta 7925-9.5	CC SLC17B
		T+1:03 SRM 1-6 out
		T+1:05 SRM 7-9 on
		T+1:06 SRM 1-6 sep
		T+2:08 SRM 7-9 out
		T+2:11 SRM 7-9 sep
	1851:31	T+4:23 MECO
	1851:39	T+4:31 Stage 1 sep
	1851:45	T+4:37 SES-1
	1852:04	T+4:56 Fairing
	1856:40	T+9:32 SECO-1	167 x 167 x 29.74
	1911:30	T+24:22 SES-2
	1913:12	T+26:04 SECO-2	163 x 4170 x 29.7?
	1914:05	T+26:57 St 2 sep
	1914:42	T+27:34 TES
	1916:10	T+29:02 TECO	179 x -86410 x 29.73
	1920:52	T+33:44 Yo yo deploy
	1920:57	T+33:49 Stage 3 sep
	1924:42	T+37:34 Target interface point
		Delta SES-3 depletion	153 x 4145 x 24.0
2005 Jan 13	0407	Pass EL1:4
2005 Jan 13	2100?	Pass lunar orbit
2005 Jan 17	1551	Leave Earth sphere 1.5Mkm
2005 Jan 19		Range 1.9Mkm
2005 Feb 1			544.14d 0.9809AU x 1.6276AU x 0.64
2005 Feb 11	1900	TCM-1 28 m/s
2005 May 5	1900	TCM-3A 95s 5.05m/s
2005 Jun			545.83d 0.9764AU x 1.6378AU x 0.48
2005 Jun 23	1900:00	E-11d TCM-3B 6m/s
2005 Jul 3	0000	TCM-5
	0600	Impactor release E-24h	0.9842 x 1.6405 AU x 0.49
	0613	Flyby TCM, E-23h48m, 101m/s 14m
	0616	Impactor detumble
	0627	TCM completed
2005 Jul 4
		E-2h autonav on
	0415	ITM-1 E-100m 1.3m/s 21.5s 3.1 kg,
	0510	ITM-2 E-35m 0.4 kg 2.2m/s, range 21600 km
	0532	ITM-3 E-12min 2.3m/s 44s 0.4 kg, range 7700 km
	0544TDB	Enter Tempel 1 sphere
	0546:02TDB	Impact at 10.298 km/s
	0559:49	Flyby Tempel 1 TCA 500 km
2005 Jul 20		TCM-6 900s
2006 Jan		DI reactivated
2007 Jan 1			0.981 x 1.638 AU x 0.66
2007 Sep 24		DI reactivated, renamed EPOXI, Cruise-1
2007 Nov 1		DI TCM-9
2007 Dec 3		EPOCh observations begin
2007 Dec 27	0308	Enter Earth Sphere 1.5Mkm
2007 Dec 29	0000?	Enter Earth SOI
2007 Dec 31	1930	Earth flyby	15566 x -95379 x 19.8
2008 Jan 3	1400?	Leave Earth SOI
2008 Jan 5	1154	Depart Earth sphere 1.5Km
2008 Jan 26		Cruise-2
2008 Feb 1			0.91 x 1.09 AU x 4.2
2008 Dec 1			364.88 0.909 x 1.090 AU x 4.2
2008 Dec 25	0445	Enter Earth sphere 1.5Mkm
2008 Dec 29	2142	Earth flyby 43450 km R=49828km	43449 x -122772 x 92.81
2009 Jan 1	1800?	Leave Earth sphere
2009 Jan 1			368.07d 0.982 x 1.027AU x 6.6
2009 Jan 3	1456	Leave Earth sphere 1.5Mkm
2009 Jun 1			367.45d 0.982 x 1.026AU x 6.6
2009 Jun 27	0021	Enter Earth sphere 1.5Mkm
2009 Jun 29	0741	Distant Earth pass at 1.34Mkm
2009 Jul 1	1457	Depart Earth sphere
2009 Aug 1			365.26d 0.975 x 1.025AU x 6.5
2009 Dec 26	0335	Enter Earth sphere 1.5Mkm
2009 Dec 28	1018	Distant Earth pass at 1.32 Mkm
2009 Dec 30	1657	Depart Earth sphere 1.5Mkm
2010 Feb 25			363.07d 0.983 x 1.029AU x 6.6
2010 Jun 23	0144	Enter Earth sphere 1.5Mkm
2010 Jun 24	2345	Enter Earth sphere
2010 Jun 27	2203	Earth flyby 30480 km	30480 x -114582 x 103.1
2010 Jun 30	0000	675000 km range
2010 Jun 30	2000?	Leave Earth sphere
2010 Jul 2	1806	Leave Earth sphere 1.5Mkm
2010 Aug 1			420.18 0.975 x 1.221 AU x 3.2
2010 Sep 5		Comet Approach Phase, begin imaging
2010 Sep 29	1800	TCM-20 60s 1.5m/s
2010 Oct 27	1800	TCM-21 60s 1.6m/s
2010 Oct 28		Comet perihelion 1.06AU
2010 Nov 2	1500	TCM-22 7s 1.4m/s
2010 Nov 4			0.975 x 1.219 x 3.2
	1359:31UTC	750 km 103P/Hartley-2 flyby	0.969 x 1.220 AU x 3.2 OWLT=8.8min
2010 Nov 30		End comet encounter phase
2011 Nov 24		Targeting burn 140s 9m/s
2011 Dec 17			0.969 x 1.209 AU x 3.2
2012 Oct 4		Targeting burn for 2002 GT
2013 Aug 11		Loss of contact with DIF
2020 Jan 4	0508	Flyby of (163249) 2002 GT at 320 km?

The science goals are to study the mantle depth, interior composition and structural properties of a comet nucleus, and to study the surface of the nucleus to find out how comets become dormant.

24 hours before impact, the impactor separates from the flyby spacecraft. Impact is at 10.2 km/s. The KE of impact is 18 GJ or 4.5 tons of TNT.

Impactor is 370 kg and is made largely of copper (since Al would contaminate the spectrum of the debris flash). Size is 1.0m long and 1m dia.

FLyby + impactor is total of 3.3 long 1.7 wide 2.3 high. pentagonal cylinder + panel + science platform.

Flyby:

Payload:

• Debris shield

• AOCS Hydrazine with 190m/s dV, 5 kNs total

• HRI High Resolution Instrument

  • Visible CCD camera 0.30m, f/35, FOV 0.1 deg

  • IR spectrometer 512 x 256 HgCdTe array, 1-5 microns

  • Special imaging module

• MRI Medium Resolution Instrument

  • Multispectral CCD camera 0.12m aperture, f/17.5, FOV 0.6 deg