Tuesday, December 14, 2010

Meeting the Challenge of Air Traffic Control Staffing

The FAA must match the number of controllers to the correct facility depending on traffic volume and workload. How can the FAA best meet this challenge?

If the FAA’s drive to transition the air traffic control system from one of control to more of a management model is accomplished, this alone should assist them in filling the ranks of what is known informally as one of THE most stressful jobs to be had. Due to the stress level of some of the Centers, there is an imposed age limit on new hires. If the stress can be reduced though a management model, perhaps that artificial limit could be raised, opening up a larger pool of candidates.
Automation will play a central role in this transition. The old guard who were not raised on technology the way today’s young people have been, have an innate fear of technology; fear of it failing for whatever reason.

Fear has been a factor in any number of transitions from older methods to newer; recall buggy whip makers’ aversion to the newfangled automobiles of the early 20th century. Although they were right in the early days—auto travel was only for a very few, and was fraught with dangers and unknowns not faced by the horse-and-buggy crowd. That eventually changed with more reliability derived from improvement of vehicles. The same is true for newfangled computers and equipment being developed within the Nextgen framework.

Communicating to prospective employees for air traffic control the efforts being undertaken in modernizing the air traffic control system is a must if new talent is to be attracted. I don’t think money in itself is a motivator. The reporter even commented on that concerning the facility in Westbury that even with a $100,000 signing bonus, there were few takers. The promise of exciting work with modern equipment that is able to maintain its currency, but the stress historically associated with the job removed or reduced, may be the better attractant.

One thing for sure, the FAA can no longer depend on people flocking to the controller job market simply because it’s in the exciting field of aviation. Anecdotally, I would relate the condition of dress of the flying public today as compared to pre-deregulation days as partial proof that this is no longer the case. Aviation itself no longer holds the exotic draw it once had. Drawing on today’s penchant for high-technology video gaming that is very popular with this day’s generation is how the FAA, along with other industry segments, must attract workers. Younger workers don’t have memory of a world without gaming, iPods, instant networking, etc., and generally have no desire for “horse-and-buggy” ancient technology—there’s not enough time to wait for that old stuff. Let’s go! So, the FAA has to continue its modernization, the public at large needs to remain in the loop on the upgrades and their advantages, and the money required to keep those advantages; all this requires communication.

Monday, November 15, 2010

Aircraft Cost Comparison Example

The following is an example of my own research of a hypothetical aircraft owner contemplating replacing an existing aircraft. It has no bearing on any real circumstance.


The owner/pilot of an existing Mitsubishi MU-2 turboprop aircraft desires to upgrade his current aircraft that is used for business and personal trips. The majority of flight is from the home base in Denton, Texas (airport identification KDTO), a single runway field with a length of 6,000 feet. The new aircraft, however, must be able to utilize a 5,000 foot runway. Ninety percent of his flights are within a 500 mile radius of Denton.

Additional trip considerations include Carlsbad, California (KCSQ), Monterrey, Mexico (MMMY), and Christmas holiday trips to St. Croix, Virgin Islands (TISX).
A maximum cash outlay of $5M (USD), including costs of selling and/or trading the current aircraft, has been set by the owner. Other aircraft specification requirements include a must-have stand-up lavatory, a minimum cabin height of five feet, and a capacity to carry eight passengers and their personal gear, exclusive of crew.

The reason for this evaluation is to select a jet aircraft to replace the MU-2 that will perform the skeletal requirements provided by the owner, and remain within the budgetary constraints; while at the same time provide enough extra capacity for future needs.

The aircraft chosen for this mission is the Hawker 800XP, a proven model, derived -from the Hawker 700. Selected data for this choice is in the following narrative.


The owner uses his existing aircraft flying out of his home base of Denton, Texas, Denton Municipal Airport. It is a single-runway field with a length of 5,999 feet (information available at Airnav.com); however, the new jet will be required to use only 5,000 feet, presumably to access smaller fields for better business utilization of the owner’s time and resources. Personal travel will use a portion of the flight time of the new aircraft. Business use constitutes approximately 324 hours annually, including a block of approximate flight time for personal use of 30 hours. Presumably, flight time will grow as the new jet proves its usefulness.

Current aircraft performance and payload is not suitable for the future needs required by the owner, as the MU-2 is configured to carry a maximum of seven passengers, with a useful payload with full fuel of approximately 1,275 lbs. (Laver, 2010) A larger payload is required for the owner’s new specifications (eight passengers with an assumed 40 lbs. of baggage each is about 1,680 lbs.).

The MU-2 range of 1,275 nautical miles compares to the Hawker’s at nearly 2,600 miles (see Table 3 below). The limited range of the MU-2 would require two hops to reach St. Croix (a hop distance of 989nm each). 
Table 1: Direct Operating Costs MU-2
Item Cost per Hour
Fuel(1) (89 gal. per hr. fuel burn) $536.67
Maintenance Labor 136.84
Parts 132.91
Engine restoration 138.44
Component overhauls 58.43
Landing fees/parking 9.55
Crew expenses 30.00
Supplies/catering 24.00
Total $1,066.84

Note: 1. Fuel at $6.03/gal. (Huber, 2008)

Although the hourly cost is less than the Hawker 800, it is an older airframe. Due to its reputation, albeit undeserved, as a plane prone to crashes (Unknown, 2008), it has not been privy to modern upgrades as other aircraft of similar age.

The current value of the MU-2 is a necessary component of this report, therefore a search of MU-2 aircraft for sale was made from the website of Avbuyer.com, (Avbuyer, 2010) returning an average price for the aircraft at around $600,000, with an average age of 32.5 years (seven aircraft were considered).

Table 2 MU-2 Used Aircraft Summary (partial)
Mitsubishi MU-2 Price Comparison

Average Age: 32.5 (years)
Average Hours: 7,255 (total time on the airframe in hours)
Average Price: $599,286

Funds must be set aside to prepare the MU-2 for sale, including inspections, appraisals, listing costs and advertising, and flight time for previewing by prospective buyers. These funds must be a portion of the $5 million dollar outlay limit set by the owner. Stories of the MU-2 as an unsafe aircraft have been disproven; (Searles, 2008) pilot error is to blame. Owners of these aircraft, transitioning from piston twin aircraft to this turboprop aircraft were not wise to the characteristics of a turbine powered airplane, (Goyer, 2010) and thus would find themselves “behind the power curve,” pushing full throttle too late for the turbines to wind up and provide proper power before the airplane contacted the ground. These concerns, and anecdotal stories passed around hangar bays, may hinder the sale of the existing MU-2 with the effect of remaining too long on the market, so funds must be available for this contingency.

The new jet aircraft will require a range of 2,000 miles (find distance information at Airnav.com) in order to reach the St. Croix airport without a refueling stop. With the owner’s requirement for 5’-0” headroom and stand-up lavatory, a mid-size cabin jet will be needed. 


The key mission of an airplane for this owner is local, five hundred mile and closer trips for his business use. Airports in more remote areas will have shorter fields that may accept jet aircraft, but must have fields shorter than 5,000 foot in length. Some trips may have a full complement, which requires the aircraft have the ability for a short-field landing, and similar for takeoff—landings are generally shorter than takeoffs. The area surrounding Denton and other places like Monterrey are generally hot weather airfields, and above sea-level altitudes, two aspects of flying that are most critical to safely piloting an aircraft (hotter, humid air is less dense providing less lift capability and must be accounted for in aircraft performance).
Secondary missions are personal trips to vacation locales, or other non-business trips where the aircraft may carry a full complement. A long hop to the one of the owner’s preferred destinations, St. Croix, has the other considerations of amount of fuel available based upon the loading of other items (people and baggage).


For consideration, a Hawker 800XP is evaluated herein. A jet listed for sale at Controller.com (Leading Edge Aviation Solutions, 2010) is a 1999 model with a listing of $4.295 million. The aircraft has a total of 6,832 hours with 4,765 landings. That is approximately 1.43 hours per flight, which indicates an average flight distance of about 575 miles. This particular aircraft appears well-suited to satisfy the owner’s key mission requirements, that ninety percent of flights will be approximately 500 miles in length.

Table 3 Selected Flight Data (Jane's, 2010)
Hawker 800/850
Payload w/maximum fuel 1,790 lbs
Long-range cruising speed at FL390 402 kts
Time to FL390 at MTOW 20 min
T-O balanced field length at MTOW 5,030 ft
Range w/6 passengers, NBAA Reserves,
at long range cruise 2,598 miles

Notes: Kts = knots; MTOW = max takeoff weight; NBAA = Nat’l Bus’n Aviation Assoc.;
T-O = Takeoff

Table 4 Direct Operating Costs 800XP:

Fuel(1) (291 gal. per hr. fuel burn) $1,754.73
Maintenance Labor 133.50
Parts 126.06
Engine restoration 320.23
Thrust reverser 3.21
Aux. Power Unit allowance 35.81
Landing fees/parking 23.10
Crew expenses 70.00
Supplies/catering 36.00
Total $2,502.64

Note: 1. Fuel at $6.03/gal. (Anonymous, 2008) Figures based on 324 hours annually

Table 5 Annual Fixed Costs 800XP:

Captain $100,100
Copilot 72,000
Burden 51,630
Insurance – Hull 26,910
Insurance – Admitted Liability 1,750
Insurance – Legal Liability 13,750
Recurrent Training 47,200
Aircraft Modernization 35,000
Charts Service 4,166
Refurbishing 28,480
Computer Maintenance Program 9,500
Weather Service 700
Total $425,866
Note: (Anonymous, 2008) 

The total annual operating costs for the Hawker will be approximately $1,236,221. This compares with $623,640 (Huber) for the MU-2, $612,581 more, or nearly a 100% premium. However, there are other considerations. Based upon projected yearly flight time, the MU-2 can only provide approximately 89,100 miles of travel (324nm at 275kts), or $6.99 per mile, whereas the Hawker can provide over 130,000 miles of travel for the same block of hours (402kts), or $9.49 per mile, only a 35% premium in hourly costs. Also, trip times will be reduced using the jet and one’s perception of the value of time is a contributing factor in justifying the additional hourly costs of the jet.

Table 6 (below) lists a comparison of the present value for the jet comparing purchasing vs. leasing. The actual discount rate will depend on the owner’s credit worthiness; these data are for comparison only.

Table 6 Present Value Purchase vs. Lease
6% Finance Rate on $4,577,6001 1.0% Lease Rate on $5,154,0001
1 $4,440,272 $4,985,800
2 4,211,392 4,728,800
3 3,936,736 4,420,400
4 3,753,632 4,214,800
5 3,524,752 3,957,800
6 3,295,872 3,700,800
7 3,158,544 3,546,600
8 2,929,664 3,289,600
9 2,792,336 3,135,400
10 2,655,008 2,981,200

Note: 1. See also Table 7 (Al Conklin, 2005)

The present value of money is least for the financing option. The residual value of the Hawker is expected to be $2,019,045 (51% of its current price in ten years). (Al Conklin, p. 185)

The jet can either be purchased outright or leased. Purchasing leaves ownership of the aircraft to the purchaser, leasing will leave ownership to the leasing company (whoever that may be). Interest rates are low in today’s economic climate, and may remain rather low for the next several years; of course, this can only be surmised. For comparative purposes, however, lease rates of up to 1.1% are compared to a finance rate range of five to eight percent, as shown in Table 7:

Table 7 Financing vs. Lease Payments
5% Finance rate $437,329
6% $457,760
8% $500,258
.9% Lease rate $463,860
1.0% $515,400
1.1% $566,940
Note: Assumed 20% down payment for financing; 100% lease for financing.

If interest rates remain low, financing with a down payment may be the better course of action. Using a 6% financing rate and 1.0% lease rate Table 8 below compares the costs over a ten year span:

Table 8 Ten Year Cost Analysis
Finance at 6% Interest $4,577,600
Operating Costs 5,845,835
Residual Value 2,019,045
Net Costs 10 Years 8,404,390
Annual Cost of Ownership 840,439
Cost per Hour (324 Hours) 2,594

Anecdotal stories concerning the 800XP, along with some relevant data, indicate the aircraft is well-liked by the users and owners of the jet. An analysis by Fred George of Aviation Week (George, 1996) paints a good picture of the aircraft handling and flight characteristics, range, payload and other pertinent specifications, and comfort and convenience features provided by the aircraft, and the article is generally praise worthy of the aircraft.

Based upon the preceding analysis, and opinion of an aviation writer, the 800XP offers one of the most comfortable interior environments for its passengers (George, 1996). The Hawker mid-cabin jet series has always offered a more generous cabin than competitors. The lavatory offers hot and cold water, and is externally serviced. Baggage storage, however, is all inside the cabin, although there are two large storage closets for bags.

The 800XP fits within the specified budget with funds remaining to sell the existing turboprop aircraft. The 800XP will provide the service required, is able to reach the destinations desired, is a worthy and able platform with high marks from within the aviation community. This aircraft fulfills the requirements of the owner.

Al Conklin, B. d. (2005). Aircraft Acquisition Planning. Orleans: The Conklin & de Decker Institute of Aviation.
Anonymous. (2008). Hawker 800XP. Orleans: Conklin & de Decker.
Avbuyer. (2010). Business Turboprops. Retrieved 2010, from Avbuyer.com: http://avbuyer.com/aircraft/Results.asp?ListId=2&ManId=107&ModelId=740&Corp=true&Gen=
George, F. (1996, June). Hawker 800XP. Aviation Week .
Goyer, R. (2010, may 31). Making the Leap from Pistons to Jet. Flying .
Huber, M. (2008, February 1). Mitsubishi MU-2. Business Jet Traveler .
Jane's. (2010, January 21). Hawker 800 and 850. Retrieved June 9, 2010, from Jane's All the World's Aircraft: http://www4.janes.com.exproxy.libproxy.db.erau.edu
Laver, M. (2010). MU-2 Model Comparison. Retrieved 2010, from Air1st.com: http://air1st.com/shortbody.php
Leading Edge Aviation Solutions. (2010). Listings Detail. -Retrieved 2010, from Controller.com: http://www.controller.com/listingsdetail/aircraft-for-sale/HAWKER-800XP/1999-HAWKER-800XP/1148724.htm
Searles, R. A. (2008, May 1). Special Rule Sets New Requirements for MU-2B Operators. Business & Commercial Aviation , p. 242.

Friday, October 8, 2010

Mission Galileo

Thought you might like to see what I'm working on in college...

The original target launch date for the Galileo mission was the spring of 1986. Due to the events of January 1986 and the Shuttle Challenger disaster, the Galileo mission did not begin until October 18, 1989. The launch trajectory was modified to use three planetary flybys in order to reduce fuel requirements in favor of payload: one past Venus and two past Earth, to gain enough energy for the trip to Jupiter, since the original date was scrapped. Along the way, Galileo provided some close-up photographs of asteroids (see Figure 1 below). On October 29, 1991, Galileo made the first fly-by of an asteroid, coming within 1,600 kilometers (1,000 miles) of Gaspra, first named by Grigoriy N. Neujamin in 1916. It is classified as an S-type asteroid, mostly likely made up of metal-rich silicates and perhaps even bits of pure metal. Its irregular shape suggests it is of recent origin, breaking off from a collision with a larger body (Hamilton, 2009).
Upon reaching Jupiter, it released the atmospheric probe, the main thrust of the mission. The probe lasted long enough to provide a great amount of data. For one, the atmospheric sample found the main constituents of hydrogen and helium to be in similar proportion as found in samples taken from the Sun. This data provides important clues as to the origin and makeup of other planetary bodies in our Solar System. An interesting observation was the scarcity of oxygen in the samples taken, indicating that Jupiter is drier than once postulated (Young, 1998).
The Orbiter remained around Jupiter more than fourteen years in contrast to its planned stay of two years, providing great amounts of data yet being researched. The mission far surpassed its desired goals, and provided information useful to future planetary missions.
The Galileo orbiter was a first of its kind design utilizing a “dual-spin” technology: two separate satellite types combined into one unit. Previous missions, such as Pioneer, used a simple rotation of the entire craft to maintain balance and direction, and allow more data retrieval of particular fields of data. This was not useful for the remote sensing capabilities required by some of the Galileo mission parameters, as obtained using three-axis satellites like the Mariners and Vikings. The combined dual-spin design of the Galileo spacecraft provided both abilities, which were useful for the measurements taken during flybys and other times when focusing on particular elements (W.J. O'Neil, 1983).
Providing both types of data gathering in one satellite produced a challenging engineering design problem: how to transfer data and power between the two units. This problem was resolved by using two types of connecting rings, a slip ring for transfer of power between the two sections, and rotary transformers for the signal (data) transfer (W.J. O'Neil, p. 3).
The spacecraft consisted of a spun section and a de-spun section. The spinning section provided regular sampling of fields and particles; the de-spun section provided inertial stability and allowed a platform for remote sensing. Communications were originally planned using a furlable, high-gain antenna (HGA) for data transfer rates of 134 kb/s (kilobytes per second), similar to antennae used with tracking/data relay satellites—a proven system (W.J. O'Neil, pp. 2-3). However, this ‘proven’ system hit a snag upon launch. It was determined that stresses during the launch damaged one of the holding clips used to keep the antenna in an un-furled position while stowed, then upon release from the launch vehicle, allowed the antenna to open. The clip failed and left the antenna in its stowed position. It left engineers with only one alternative: utilizing the low gain antenna as their main communication link between mission control and Galileo (see Mission Overview below).
The Probe consisted of two units, a deceleration module that would position the second portion of the mission element of the Probe, the descent module. The descent module contained instrumentation to measure atmospheric pressures and density, helium abundance, and a net flux radiometer (to measure how deep solar energy and planetary emissions penetrate the Jovian atmosphere), among other instruments (W.J. O'Neil, p. 4).
The reason for an exploration of Jupiter draws from our understanding of the origin of the solar system (in 1975 from the National Academy of Sciences recommendations of in-depth studies of the universe) and that Jupiter, being the gaseous planet it is, could be representative of a primordial solar system. Since it retains what is considered a primordial composition, it is considered a better “cosmological ‘laboratory’” than the other planets (W.J. O'Neil, p. 1).
As the orbiter remained in a prolonged voyage around Jupiter proper, mission controllers used each Jovian satellite encounter to grab a gravity assist to provide it the energy to make the next Jovian satellite encounter. This process provided repeated visits to each of the four major moons of Callisto, Europa, Ganymede and Io but also provided the desired changes in the periods and orientation of orbits to allow the next satellite flyby. “This satellite-gravity-assist-tour is the foundation of the Orbiter mission design.” (W.J. O'Neil, p. 1)
Information gathered from this most important mission to Jupiter continues to provide insight for missions to come. One important consideration for future missions was drawn from the demise of the Galileo orbiter. Unlike the Probe, whose planned mission was a plunge into the atmosphere whereupon it would disintegrate due to the intense pressure of the Jovian atmosphere, it was agreed to end Galileo in a similar fashion for another reason: evidence of water. Evidence of water was gleaned on one of the Jovian satellite flybys of the moon Europa. This was given as the reason to end Galileo’s mission with a purposeful, though un-planned, entry of the orbiter into Jupiter’s atmosphere in order to keep Europa from being contaminated, and maintain its purity for future exploration (E.E. Theilig, 2003).
As we delve deeper and deeper into our Solar System and into deep space, consideration for the well-being of other planets must remain a priority. It is similar to how we approach the Galapagos Islands here on earth, islands that are left undefiled and un-developed in order to preserve that ecosystem for future non-destructive exploration, and to leave it for future generations’ enjoyment.
Another valuable lesson taken from this historic mission is that of longevity of a spacecraft’s lifespan. The Galileo orbiter was designed for a much shorter mission than the fourteen years it remained productive, and even longer, if not for the consideration given Europa. Without purposefully designing for a fourteen year mission, the quality that was put into this particular craft allowed it to survive much longer than planned. This needs to remain a goal for all future spacecraft.
Another discovery by Galileo that provides important navigation information for future missions is the star Delta Velorum is actually a variable star, not a single entity. Delta Velorum is a grouping of five stars, of which one pair is binary. Deep space satellites identify navigable stars from their apparent brightness at any given time. Knowing if a certain star is variable (and changes in apparent brightness) is information that is highly useful for future missions, since changes in the brightness of a particular star could cause incorrect interpretation of navigable data for a satellite or spacecraft (E.E. Theilig, pp. 338-339).
Studies of Io’s volcanic activity indicated it was produced by conditions that are more similar to an early Earth. Original theories of the origin of Io’s volcanic activity from data gathered by the earlier Voyager mission were that it was produced by melted sulfur. Distant observations showed temperatures too high for this theory. The close observations of Galileo proved that Io’s core was silicate based, and heated by the gravitational tides of Jupiter (E.E. Theilig, p. 40). Observations like this could provide for go, no-go decisions as to which planet to approach for exploration or which one to avoid.
In all, the amount and type of data gathered by Galileo in its long and illustrious travels will continue to provide guidance for future exploratory missions, and the program was a major building block of our understanding of the Solar System and of space. Each deep-space mission builds on the next in a block by block fashion, giving a leg up on the next successive mission as we reach out beyond our own planet.
One of the procedures used to overcome the effects of intransigent equipment and the harshness of the space environment was using the low gain antenna (LGA) for data transmission when the main antenna failed to perform to its design. It was eventually determined that either one or both of the rib restraint pins that kept the antenna folded during launch remained in their receptacles, preventing the antenna from being unfurled (Slatman, 1994). Although it was the designed method to be used for the mission, reverting to and then using the LGA required other adjustments as well: on board buffering of data prior to transmission and extensive processing, which in itself stood to overload onboard equipment. This required having an Earth-bound replica of the orbiter to perfect the processes used to successfully retrieve data from Galileo (Bruce A. McLaughlin, 1994).
“To allow extended high rate data acquisition without overflowing the multi-use buffer the Buffer Dump to Tape function has been implemented.” (Bruce A. McLaughlin, p. 1042) This was a method devised whereby the onboard Data Memory System (DMS - a type of tape recorder) temporarily stored the data that overflowed the buffer, since the speed of the downlink was sorely restricted using the LGA. It required buffer management by predicting rates of data acquisition and scheduling the buffer to dump to the DMS so that any overflow could be prevented, which could freeze the system and prevent downloading the data to mission control.
This type of foresight and engineering manipulation is something to be emulated on future missions when unforeseen events occur. This type of scenario is highly likely as space remains quite unpredictable, and is precisely why lessons learned from the Galileo mission are so valuable as we continue explorations of the Solar System.
Exposure to accumulated radiation in the further reaches of the Solar System at rates four times anticipated, far above design standards, degraded the performance of some of the subsystems. The Attitude and Articulation Control System’s (AACS) gyros, used to control the movements of the satellite and its orbital changes, suffered from this radiation, reaching degradation of nearly 100% after one particular pass by the moon Io (E.E. Theilig, 2003).
Levels of radiation beyond what we encounter close to Earth are a major concern for spacecraft, and methods of dealing with, and protecting from these levels must continue to be researched and incorporated into other missions. This will be especially true for spacecraft control systems that are quite delicate here on Earth, where our atmosphere provides a protective cocoon, and therefore must be shielded with anticipation of a very hostile environment that is completely inhospitable.
Command and Data and Data Memory Subsystems also suffered from the exposure to high levels of radiation. “Transient bus resets, presumably induced by radiation exposure…plagued the spacecraft [starting] in 1991.” (E.E. Theilig, p. 331) Cosmic particles can pass through a memory bus, impacting the electronic switches, causing them to either stop working or produce erroneous data (a “1” for a “0”, and vice versa). Software patches were written and uploaded many times to the orbiter to bypass these problems as they arose. A bus error occurs in a computer (or computer system) when its processor attempts to access memory and the location it is trying to access doesn’t exist (the system doesn’t recognize the memory location, a software error), or it doesn’t respond as designed (a hardware problem) (Unkown, 2010).
The NASA team alleviated most occurrences of bus resets by up-linking software patches that set specific memory bits to recognize certain errors as being spurious (E.E. Theilig, p. 331). Although not 100% successful, this bit of software ‘sleight-of-hand’ was able to resolve several instances where, had it not been for the patch, raw data would have been lost and commands to the spacecraft would not have been recognized at the correct times.
A glitch with Galileo that may have faded into history had digital recording media been available at that time, was the recording mechanism used to gather data and replay it at a rate to match the reduced downlink data transfer speed; essentially a magnetic tape recorder, albeit advanced enough to withstand the rigors of space. Due to radiation exposure and outliving its intended lifespan, the tape mechanism would get stuck from time to time, more so later in its lifespan. It was determined the tape was sticking at a tape guide, so a software patch was uploaded that anticipated this sticking, and allowed the moment of sticking to be bypassed. All digital recording devices used today have replaced this older technology.
Better protection from cosmic rays and higher levels of radiation will be required for future missions to shield spacecraft subsystems and allow them to fulfill their missions. A solution the Galileo team utilized to provide more protection was to place certain systems into hibernation when approaching a known high-radiation sector of space (E.E. Theilig, p. 337). Of course, this area was known since a previous pass through it had exposed the orbiter to elevated levels of radiation, providing evidence to ground controllers of its existence. In deeper space probes, this solution may not be viable if higher-radiation level spots are unknown, but it is well to keep it as an available option. It may be that deep-space probes will need planned periods of hibernation in order to bypass those known high-radiation areas, or simply to pass through portions of space prior to reaching a mission objective and to increase their longevity until the objective has been reached.
The Galileo mission was a resounding success since its original mission span was far exceeded, a testament to well-planned design and mission management. Lessons learned from overcoming the obstacles Galileo faced can be applied to tomorrow’s explorations, a building block upon which future blocks can be placed and draw direction from. As we send more and more unmanned spacecraft to explore our vast universe, lessons carried over from one mission to the next will improve success rates and mission achievements for years to come, lessons that will also be applied to manned explorations.

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Hamilton, C. J. (2009). Gaspra. Retrieved September 21, 2010, from Views of the Solar System: http://www.solarviews.com/eng/gaspra.htm
Ian A. Whalley, J. C. (2003). Development of a Parachute Mortar Cartridge for the Galileo Jupiter Probe. Hunstville AL: AIAA.
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Slatman, J. (1994). Optimizing the Galileo Communication Link. Pasadena CA: Jet Propulsion Laboratory.
Unkown. (2010). Troubleshooting Bus Error Crashes. Retrieved September 5, 2010, from Cisco.com: http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_tech_note09186a00800cdd51.shtml
W.J. O'Neil, R. M. (1983). Galileo Mission Overview. Reno NV: AIAA.
Young, R. E. (1998). Galileo Mission (Jupiter). Access Science.