Minimize Genesis inflatable space complex

Genesis inflatable space complex program of Bigelow Aerospace

The entrepreneur Robert T. Bigelow of Las Vegas, Nevada (USA), started his private company Bigelow Aerospace in 1999 with the vision to change the current cost and availability involving commercial and public use of non-habitable and habitable space complexes. The goal/commitment is to develop and operate a privately-owned inflatable space complex commercially and to be of service to a community of customers interested in space exploration and space habitats.

In the late 1990s, NASA was engaged in the development of TransHab, a large inflatable habitat in space who's multi-layer shell was based on Kevlar high-strength fibers (TransHab requirements called for an inflated volume of 340 m3 , 11 m in length and 4.3 m in diameter, and a launch mass of 13,200 kg) for protection from orbital and meteoroid debris. TransHab was intended as a replacement for the already existing rigid International Space Station crew habitation module. However, the US Congress (and NASA) cancelled the TransHab project in 2000 due to budgetary constraints.

In 2002, Bigelow Aerospace signed a NASA Space Act Agreement contract with the Technology Transfer and Commercialization Office of NASA/JSC. That agreement (exclusive license) enabled the private group and NASA to work together on evaluating next generation inflatable/expandable space module technology. Thus, Bigelow Aerospace started to pursue a development scheme for a civilian space complex - using the patents developed by NASA. The TransHab concept originated at NASA/JSC in 1997 as a possible design for inflatable living quarters on future Mars-bound spacecraft, and was led by William Schneider who became a Bigelow Aerospace consultant after his retirement from NASA. 1) 2) 3) 4)



Inflatable spaceborne structures have been used since 1960 with the launch NASA's ECHO series experimental communication and geodesy satellites. These balloon satellites of 30 m diameter (ECHO-1A launch Aug. 12, 1960 available until 1968, ECHO-2 launch Jan. 25, 1964 available until 1969) were deployed from a packing container 0.67 m in diameter using inflation gas.

• Over 30 launches of inflatable spheres occurred during the period from 1960 to 1971 with some remaining in orbit for over 11 years. Several of the early balloon satellites failed during the inflation event. Some of these failures were attributed to lack of control of the inflation process. Modifications were made to the packing and inflation procedure which lead to success with subsequent flights. Most of the early research on space inflatables centered on methods of making the structure rigid after inflation.

• In 1996, the spaceborne NASA IAE (Inflatable Antenna Experiment) was flown on SPARTAN-207 of the Shuttle mission STS-77 (May 19 - 29, 1996), a small free-flying satellite, made up of four major components: lens, torus, struts, and body. The experiment was conceived to verify the accuracy of an inflatable off-axis parabolic lenticular antenna structure deployed in space and to demonstrate its performance.

• ARISE (Advanced Radio Interferometry between Space and Earth) is a NASA/JPL astronomy satellite mission in planning consisting of a 25 m diameter radio telescope (an inflatable structure with a very thin reflecting surface that does all the work in collecting light from the cosmos) in a highly elliptical Earth orbit (HEO). The new lightweight telescope architecture is called DART (Dual Anamorphic Reflector Telescope). The DART concept makes use of two parabolic, cylindrical trough-shaped reflectors oriented with respect to each other to produce a point focus. Since each reflector contains only a single simple curve, the mirrors can be formed by tensioning a reflective foil over a frame that has a parabolic contour along one axis. The use of an extremely low-mass membrane for the reflective surfaces reduces the mass of the telescope.

Major advantages of using inflatable elements in space are their high packaging efficiency, extremely light weight, high deployment reliability, and low cost. These favorable attributes make inflatable space structure technology as one of the emerging/enabling technologies in the early 21st century that can potentially revolutionize the designs and applications of large space structures. The spectrum of potential applications, ranges from remote sensing (radars, radiometers, interferometers, telescopes, etc.) to radio astronomy, communications, WPT (Wireless Power Transmissions), as well as to habitable space complexes. In particular, inflatable modules provide an 'easier to launch' compact form to be accommodated in existing launch vehicles.

Bigelow Aerospace (BA) is planning on a series of inflatable structure tests in space. The goal is to evolve eventually into the deployment of the Nautilus outpost in Earth orbit. The planned full-scale Nautilus Space Station of Bigelow Aerospace will have a mass of 20-23 tons and a size of 13.7 m in length and 6.7 m in diameter, providing a usable volume of 330 m3 when inflated.

The business model of Bigelow Aerospace focuses on two classes of customers: “sovereign clients,” i.e., foreign governments looking to jumpstart their own space programs; and “prime clients,“ major corporations interested in leasing module space for various business purposes. The idea of Bigelow is based on the assumption that there are far more countries with an interest in having their own astronaut corps, then there is capacity by existing spacefaring nations to accommodate them. 5) 6)




Genesis-1 is a technology demonstration mission (pathfinder) for an inflatable orbital habitat family, representing an initial module for the planned inflatable Nautilus space station structure by Bigelow Aerospace. The privately built and financed habitable structures are intended to be available for research, manufacturing and other uses, including lodging for future space tourists. The future business the Bigelow Aerospace is interested in - is to provide in particular additional destinations for astronauts from other countries (than the USA and Russia), as well as all the related services needed for those astronauts and their space agencies.

The Genesis program utilizes space vehicles in LEO (Low Earth Orbit) with the objective of testing and validating the technologies necessary for the deployment of expandable space habitats. The primary objective is to demonstrate inflation and deployment in LEO. 7)

Secondary objectives:

• Develop core competency to build, launch and operate satellites and space complexes

• Proof of concept for folding, restraint, and core structure

• Evaluate the durability of soft goods

• Long-term effectiveness of the MMOD (Micro Meteorite Orbital Debris) shielding

Tertiary (mission creep) objectives:

• Revenue and interest-generating payloads

• Evaluate the performance of various off-the-shelf (literally) electronic components

• Obtain long-term evaluation of power systems

• Evaluate the radiation environment.


Figure 1: Illustration of the deployed Genesis-1 spacecraft (image credit: Bigelow Aerospace)


Genesis-1 has a launch mass of about 1,360 kg and a size of 4.6 m in length and 1.6 m in diameter at launch. The spacecraft architecture features an expandable outer surface that is wrapped around a central core at launch and expanded through air inflation in orbit. The skin is made of several layers that include proprietary impact-resistant materials.

The flexible structure is designed to double in diameter once in orbit. The one-third scale hardware is to produce important data regarding multiple features of a full-scale spacecraft (Nautilus). The Genesis-1 spacecraft is being pressurized with nitrogen, but later units will use an oxygen/nitrogen mixture. The Genesis design of future vehicles will also include windows and an airlock simulator with key seal interfaces. One window is contained in the shell structure.

The internal core structure of the spacecraft contains the following elements:

- Battery and payloads in interior of spacecraft

- Some avionics contained on exterior of the core structure

- Launch adapter on aft end.

The spacecraft assembly occurred at the Nevada facility of Bigelow Aerospace, followed by shipment to Russia.

ACS (Attitude Control Subsystem): The mission design provides minimal pointing requirements. The nadir aft orientation and rotation about long axis offers a benign thermal environment, a so-called ‘rotisserie’ effect. The attitude of the spacecraft is being sensed with magnetometers (2 are mounted in the forward end), and 4 sun sensors. Actuation is provided with magnetic torque rods [2 are mounted in the x (longitudinal) axis, one each are mounted in the y and z axis].

The avionics subsystem features a CAN (Controller Area Network) bus implementation developed at SpaceQuest of Fairfax, VA. Nearly every component of the spacecraft bus is a CAN-compliant device. Each has at least one on-board processor, making the spacecraft a network of smaller computers, each looking after itself and its assigned functions. From the dual BCR (Battery Control Regulators) and GPTs (General Purpose Terminals) used for collecting telemetry and controlling other powered devices and experiments, down to individual sun sensors, every CAN-compliant device onboard is networked together by the SIF (Standard Interface) cables which ferry both power and data between all the nodes. The CAN bus utilizes a ring topology to minimize excess cables, while providing a fault-tolerant bus geometry adding a physical layer of protection on top of the individually fault-tolerant CAN-compliant devices. 8)


Figure 2: Internal core structure surrounded by inflated volume (image credit: Bigelow Aerospace)



Figure 3: Alternate view of Genesis-1 (image credit: Bigelow Aerospace)

MMOD (Micro Meteorite Orbital Debris) shield description:

- Multi-layer insulation with interstitial foam to provide loft

- Restraint layer–load bearing (essentially metallic foil)

- Air barrier

- Folded in launch configuration, restrained with straps.

Deployment systems:

- Retention straps released using pyro cutters

- Solar array deployment

- All deployment and inflation controlled by onboard flight computer.

Inflation: Genesis 1 features a single tank with redundant solenoid valves.

RF communications: All data is recorded onboard the spacecraft and downloaded as encrypted files during passes over ground sites. The onboard data sampling rate can be scaled up and down as necessary to prevent build up of data.

- Redundant omni-directional antennas on each end of the spacecraft

- UHF/VHF for duplex command and telemetry

- S-band for photo downlink.

The spacecraft data is collected and archived at the Las Vegas site. For the Genesis-1 launch, support was provided with two ground stations, located in Virginia and Nevada. Both stations provided a UHF/VHF uplink capability. The S-band antenna is equipped with a 6 m dish.


Launch: A successful launch of Genesis-1 took place on July 12, 2006 on a Dnepr-1 vehicle (launch provider ISC Kosmotras). The launch site was the Dombarovsky Missile Site, Yasny (southern Ural mountains) in the Orenburg region of Russia. The Genesis launch was inert with auto activation on separation.

Orbit: near-circular orbit of 556 km x 583 km, inclination = 64.5º, period = 96 minutes.

Spacecraft expansion (inflation): After attaining orbit, computer-controlled air-pressure tanks activated and expanded the pre-folded structure into its watermelon shape: after expansion the spacecraft attained 2.54 m in diameter (inflation rate: 15 minutes).

The spacecraft's planned operational lifetime is five years, during which technicians will determine if Genesis can maintain the proper internal air pressure and temperature, whether it can withstand any collisions with space debris and micrometeorites, and whether solar radiation causes any deterioration of the airtight fabric. The tough fabric shell is made of a composite of Kevlar - used to make bullet-proof vests - and an advanced material called Vectran. Contrary to many expectations, Bigelow Aerospace anticipates that its inflatable modules will be more durable than rigid modules. The multi-layer Vectran is twice as strong as kevlar and flexible walls are more considered suitable to sustain micrometeorite impacts better than rigid walls.


Figure 4: The blueprint of Genesis-1, expanded module (image credit: Bigelow Aerospace)


Figure 5: The blueprint of Genesis-1, contracted module (image credit: Bigelow Aerospace)

Item No in Figure 4

Parameters of expanded module



Spacecraft length

4.4 m


Spacecraft diameter

2.54 m


Usable volume of spacecraft

11.5 m3


Solar arrays



Shell skin

15 cm thick, multilayer system


Communication antenna



Parameters of contracted module



Spacecraft length

4.4 m


Spacecraft diameter

1.6 m

Table 1: Overview of parameters of Genesis-1 in expanded and contracted state


Mission status:

• The Genesis-1 spacecraft is operating nominally in 2013, in its 7th year on-orbit.

- One of the greatest benefits of using inflatable habitats is the protection offered to its inhabitants from radiation. When spacecraft made from more conventional metal structures are exposed to radiation, from events such as a coronal mass ejection, a secondary radiation effect occurs. This can either be from scattering of the radiation, or the atoms in the structure itself can become excited and re-radiate. This doesn't happen with non-metallic materials used in inflatable craft outer skins thereby significantly reducing the risk to its inhabitants.

- At the heart of the inflatable technology is a material called Vectran, twice as strong as Kevlar and present in several layers of the 15cm thick skin of the Genesis craft. The flexible nature of the material results in further added safety for potential station inhabitants, a benefit supported by laboratory tests. It was found that micrometeoroids that would puncture the rigid skin of the International Space Station only penetrated half way through the skin of the Genesis craft. Because of its success so far, NASA are in talks with Bigelow for a module to attach to the ISS, called the Bigelow Expandable Activity Module. If it gets the go ahead, it could mean the first step in a new wave of space modules and craft. 9)

• The Genesis-1 spacecraft is operational in 2012 producing data (imagery, videos) for Bigelow Aerospace. It is now demonstrating the long-term viability of expandable habitat technology in an actual orbital environment. 10)

• The Genesis-1 module is orbiting Earth in 2011 transmitting data about its temperature, hull integrity, power levels, and overall health. In its 4th year on-orbit, the spacecraft is now demonstrating its long-term viability of expandable habitat technology in an actual orbital environment. In particular, the inflated structure maintains its pressure well enough to make a full size module habitable. The current orbital lifetime is estimated to be 12 years (Ref. 7).

As a consequence of Bigelow's experience with the Genesis on-orbit spacecraft - NASA is planning to investigate making inflatable space-station modules to make roomier, lighter, cheaper-to-launch spacecraft. The project is called BEAM (Bigelow Expandable Activity Module). 11) 12)

• Genesis-1 completed its 10,000th Earth orbit after 660 days in space (May 2008). It is now demonstrating the long-term viability of expandable habitat technology in an actual orbital environment.

• Initial operations indicated that the spacecraft was holding pressure after inflation (stable pressure with no leakage).

• Within hours after launch, the Genesis-1 module expanded successfully and sent back extensive data and images to the Mission Control Center at Las Vegas, Nevada.


Genesis-1 instrumentation:

Instruments on board include dosimeters, microphones, and interior cameras (13 video cameras), some of them floating inside the module. The craft contains many small items such as toys and simple experiments chosen by company employees to be observed via camera.


GeneBox is a miniature laboratory of NASA/ARC (Ames Research Center). The objective is to analyze how the near weightlessness of space affects genes in microscopic cells and other small life forms. The micro-laboratory includes sensors and optical systems that can detect proteins and specific genetic activity. 13) 14)


Figure 6: View of the GeneBox as part of the Genesis-1 payload (image credit: NASA/ARC)

Radiation monitors:

- Dose depth monitors. These are RadFETs to measure the cumulative energy deposition

- Proton monitors: SEU (Single Event Upset) measurement.


Figure 7: Photo of the radiation monitors (image credit: Bigelow Aerospace)


Genesis-1 features 18 cameras for internal and external evaluation of softgoods, some are oriented on payloads.




Genesis-2 is the second experimental pathfinder spacecraft designed to test and confirm systems for future manned commercial space modules planned by BA (Bigelow Aerospace). The Genesis-2 spacecraft is identical in size and appearance to Genesis-1, approximately 4.4 m in length and 1.9 m in diameter at launch, expanding to 2.54 m in diameter after expansion in orbit. The launch mass of Genesis-2 is about 1360 kg. The spacecraft design life is 5 years.

A number of improvements were incorporated, in particular with regard to materials and systems (S/C control), resulting in an improved vehicle. Genesis-2 is equipped with a distributed, multi-tank inflation system. This is a reliability improvement on the single-tank design of Genesis-1. 15)

Genesis-2 contains the same core attitude control and stabilization system used on Genesis-1 with improvements that provide more refined pointing control and a faster dampening of the initial tip-off rate or body rotation from rocket separation. The magnetic torque rods, magnetometer, GPS receiver and sun sensors from Genesis-1 are augmented on Genesis-2 with new reaction-wheel assemblies and a precision measurement system. The reaction-wheel system allows for the significantly faster body rate settling time and provides a technology demonstration capability needed for the larger future vehicles planned by BA.

Finally, additional layers to the outer shield of Genesis-2 were added to provide more safeguards to the vehicle and its subsystems. These additional layers offer better protection against micrometeoroid collision damage and improved thermal management, and will help characterize shielding requirements necessary for future missions.


Launch: A successful launch of Genesis-2 took place on June 28, 2007 on a Dnepr-1 vehicle (launch provider ISC Kosmotras). The launch site was the Dombarovsky Missile Site, Yasny (southern Ural mountains), in the Orenburg region of Russia. - The flight and stage separation of the Dnepr-1 performed nominally, with Genesis-2 separating from the rocket into an orbit with an inclination of 64º. 16)

Orbit (same orbit as Genesis-1): near-circular orbit of 560 km, inclination = 64.5º, period = 96 minutes.

RF communications: The ground station coverage includes sites at Las Vegas, and Virginia. New stations in Alaska and Hawaii were added for Genesis-2 to increase the contact periods with the two spacecraft to 5 hours per day. The launch of Genesis-2 requires Bigelow Aerospace to coordinate the services of multi-vehicle simultaneous operations.


Status of Genesis-2 mission:

• The Genesis-2 spacecraft is operating nominally in 2013.

• The Genesis-2 spacecraft is operating nominally in 2012 (Ref. 15).

• The spacecraft is operating nominally in 2011 (in its 4th year on-orbit) - transmitting pressure, temperature and radiation data to the mission operations staff in Las Vegas. The team is also conducting long-term testing of systems such as lighting, air circulation, and pressure monitoring systems (Ref. 7).

• Genesis-2 completed its 10,000th orbit around the Earth on April 23, 2009.

• After more than 150 days in space and 2,300 orbits, Genesis-2 has scored high grades in its first "report card." All the initial testing and checkout of the spacecraft systems have been completed.

• When the ACS system was turned on after inflation, communications stabilized within 48 hours. The spacecraft is oriented with its forward end facing Earth.

• Shortly after launch, Bigelow Aerospace had established contact with its second pathfinder spacecraft, Genesis-2. Initial data confirmed that deployment of the spacecraft, expansion (inflation of the module), and the deployment of its solar panels have been successful (Ref.16).


Genesis-2 instrumentation:

Genesis-2 includes a suite of additional sensors and avionics that didn't fly on Genesis-1. Moreover, while Genesis-1 contained 13 video cameras, Genesis-2 nearly doubles that figure to 22 cameras located on both the inside and outside of the spacecraft. Considerable effort has been made by Bigelow Aerospace engineers to improve the overall performance, reliability, and data-flow capabilities of the vision system to enhance the images from each of the 22 cameras onboard Genesis-2.

Technology demonstrations include a refined networking architecture over the Genesis-1 design, dual FireWire and Ethernet camera interfaces, and multiple new camera types including articulated cameras and a wireless camera for additional exterior shots. The Genesis-2 payload program was expanded over that of Genesis-1. This includes the “Fly Your Stuff” program, which allows customers to see their own objects floating around in microgravity.

The Genesis-2 sensor suite has been improved with additional pressure, temperature, attitude control, and radiation detection sensors. This will allow Bigelow Aerospace to better characterize the LEO (Low Earth Orbit) environment and the impact it has on spacecraft components, both interior and exterior. These new improvements also affect our revamped habitat for small-scale biological organisms and bugs. The new habitat includes new air and water-handling control systems, environmental sensors and robotic manipulators as preparation for the accommodation of larger life systems.

Also tucked aboard Genesis-2 are a Space Bingo game and Biobox filled with ant farms, scorpions and Madagascar hissing cockroaches. The Space Bingo game is chiefly aimed at entertainment, with no actual wagering involved, and is slated to begin operations a few months after launch. The Bingo Box will use fans and levers to autonomously mix and select bingo balls during games presented on the company's website. - The Biobox is a three-chamber pressurized vessel with compartments for biological specimens to be observed by onboard cameras.



Future plans:

1) The next spacecraft under development at Bigelow Aerospace is dubbed Galaxy, representing an evolutionary step between the Genesis-class modules and the standard, human-habitable complex modules. It will provide critical risk reduction as well as provide first-flight experience for technologies being developed and intended to be flown in the future commercial space complexes.

A number of technology advances will be implemented on Galaxy. These include:

• Advanced onboard avionics: Features increased performance, reconfigurability, decentralized processing, superior redundancy capabilities and “plug and play” features to speed integration and testing while improving reliability.

• ECLSS (Environmental Control Life Support System). While Galaxy will not need to support human passengers, it serves as an ideal test-bed to flight-qualify critical elements of our life- and crew-support systems in zero-gravity.

• Upgraded attitude determination and control system: The basic Genesis-class guidance, navigation and control system will be upgraded to provide greater torque-control authority and momentum management with precision attitude sensing.

• Increased communications bandwidth (capability of a real-time video downlink). This includes upgrades to the ground segment infrastructure.

• An improved, more robust air-barrier is required: This includes more damage-resistant properties. Human-factor considerations have to be addressed in the selection of materials robust enough to support frequent and intensive onboard astronaut activities.

• Power system improvements: To include larger and more efficient articulated solar arrays and high-performance battery technologies.

• Structural upgrades: Mass and stiffness efficiency improvements will be made to the primary structure and the software. These improvements will support scalability to the larger spacecraft. The addition of an access hatch and an additional, larger window/viewing port is planned.

The usable volume of Galaxy will be about 45% larger than of the Genesis predecessor spacecraft (length of 4 m, diameter of 3.3 m, usable volume of 16.7 m3).

A launch of Galaxy was planned for late 2008.

However, in August 2007, Bigelow Aerospace announced that due to rising launch costs (stated as three times more expensive than for previous launches) and the successful Genesis missions, the Galaxy spacecraft would not be launched. Instead, many of the module's systems, possibly the entire craft, will be constructed and ground tested, allowing Bigelow employees to gain further experience and potentially advance Sundancer's schedule.

2) The follow-up spacecraft of Bigelow Aerospace is dubbed Sundancer, about 45% in size (~180 m3) of the full-scale Nautilus version, with a planned launch in 2014. Sundancer is expected to have a mass of about 8,200 kg and will be equipped with life support systems, attitude control, three windows, on-orbit maneuverability, reboost, and de-orbit capability. Sundancer is planned to be BA's first manned testbed to test and confirm systems to be used in the private company's commercial space station efforts. It is also planned to form the first piece of the first commercial space station. 17)

Plans are to launch and dock a combined propulsion bus and central node to Sundancer in 2014. The bus and node would be the one Bigelow module without an expandable surface.

3) The first BA 330 module (interior volume of 330 m3 , expected total mass of 23,000 kg), previously known as `Nautilus Space Complex', is the complete, full-scale production model of Bigelow Aerospace's expandable space habitation module program. A launch of BA-330 is expected in the timeframe 2012/14.

Module type

Module name

Launch date

Launch vehicle

Mission status

Genesis Pathfinder (11.5 m3)


June 12, 2006


Operational in 2012

Genesis Pathfinder (11.5 m3)


June 28, 2007


Operational in 2012

Galaxy (vol. 16.7 m3)


Mission cancelled


Launch cancelled, tests on ground

Sundancer (vol. 180 m3)


2015 (mission cancelled)


Launch cancelled

BA 330 (vol. 330 m3)



SpaceX Falcon 9

under development

BA 2100 (vol. 2100 m3)





Table 2: Overview of the Bigelow Aerospace missions

In 2010, Bigelow Aerospace announced it had received formal expressions of interest from six governments (United Kingdom, Netherlands, Australia, Singapore, Japan and Sweden) in leasing space aboard the company’s planned inflatable space habitats that could begin launching as soon as 2014. 18)


Figure 8: Size comparison of the Bigelow Aerospace growth chart (image credit: Bigelow Aerospace)

1) T. Dinerman, “Genesis and the future space hotel,” The Space Review, July 17, 2006,

2) D. Schrimpsher, “Interview: TransHab developer William Schneider,” The Space Review, Aug. 21, 2006,

3) “TransHab Concept,”

4) “Bigelow Aerospace,” URL:

5) J. Foust, “Big plans, low prices,” The Space Review, April 16, 2007, URL:

6) L. David, “Bigelow Focuses on Space Agencies, Commercial Users,”, Space News, April 16, 2007, p. 17

7) Tom Londrigan, “Bigelow Aerospace Genesis - Testing Expandable Spacecraft in LEO,” Oct. 27, 2011, URL:

8) SpaceQuest develops avionics equipment for Bigelow Aerospace Genesis-1 pathfinder,” July 21, 2006, URL:

9) Mark Thompson, “Bigelow's inflatable space stations,” Aug. 27, 2012, URL:


11) Paul Marks, “NASA turned on by blow-up space stations,” New Scientist, March 3, 2010, URL:

12) Leonard David, “International Space Station Could Get Private Inflatable Room,”, Jan. 26, 2011, URL:

13) John Bluck, “Bigelow Spacecraft Carries NASA 'Genebox' For Tests In Orbit,” July 17, 2006, URL:

14) “Bigelow Spacecraft Carries NASA 'GeneBox' for Tests in Orbit,” Astrobiology, July 17, 2006, URL:


16) “Russia Launches Genesis 2 On Converted SS-18 ICBM Launcher,” Space Travel, June 29, 2007, URL:


18) Amy Klamper, “Bigelow Modules Draw Interest from Six Governments,” Space News, Oct. 22, 2010

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates.