OrbitalHub

Credits: Orbital

Taurus is a four-stage, inertially guided, all solid fuel, ground launched vehicle, designed and built by Orbital Sciences Corporation. In a typical mission, Taurus can inject a 1,350 kg payload in low Earth orbit (LEO).

Taurus lifted off for the first time on March 13, 1994. Since then, Taurus has conducted six of eight successful missions.

Taurus is well suited for LEO missions to a wide range of altitudes. Different orbital profiles can be attained through launches from more than one launch site. An additional fifth stage can boost the performance of the launch vehicle, making possible high energy and geosynchronous transfer orbit (GTO) missions.

Depending on configuration, Taurus can have up to 5 stages.

Stage 0 is an ATK Thiokol Castor 120 Solid Rocket Motor (SRM). Castor 120 is a commercial version of the Peacekeeper first stage. The stage is 9.06 m long and 2.38 m in diameter, with a mass of approximately 49 tons. The first Taurus used the Peacekeeper first stage as Stage 0.

Peacekeeper was an Inter-Continental Ballistic Missile (ICMB) deployed by the United States beginning in 1986. The Peacekeeper ICMB could carry up to ten re-entry vehicles, each armed with a 300-kiloton warhead (just to have an idea about the order of magnitude, that is twenty times the power of the bomb dropped on Hiroshima). The last Peacekeeper was decommissioned in 2005.

Stage 1 is an ATK Orion 50S SRM, 7.53 m long and 1.28 m in diameter, with a mass of approximately 12 tons. In the XL configuration, the stage is 8.94 m long and has a mass of approximately 15 tons. Stage 2 is an ATK Orion 50 SRM, 2.64 m long and 1.28 m in diameter, with a mass around 3 tons. In the XL configuration, the stage is 3.11 m long and almost 4 tons. Stage 3 is an ATK Orion 38 SRM. Stage 3 has a mass of around 800 kg, a length of 1.34 m, and a diameter of 97 cm.

The payload fairing comes in two versions: the 63” diameter fairing, manufactured by Vermont Composites, and the 92” diameter fairing, manufactured by Texas Composites. The fairing encapsulates and protects the payload during ground handling, integration operations, and flight. The payload mating is done late in the launch operations flow, so the designs of both fairings provide for off-line encapsulation of the payload and transportation to the launch site.

Taurus can be assembled in different configurations, depending on the specific requirements of the mission. The configurations are designated using a four-digit code. The first digit indicates the vehicle configuration (1 – SSLV Taurus with Peacekeeper first stage used as Stage 0; 2 – Commercial Taurus Standard with Castor 120 Stage 0 and standard-length Stage 1 and Stage 2; 3 – Commercial Taurus XL with Castor 120 Stage 0 and XL-length Stage 1 and Stage 2), the second digit designates the fairing size (1 for 63” fairing and 2 for 92” fairing), and the third and fourth indicate the Stage 3 motor (0 if there is no Stage 3 in configuration, 1 for Orion 38, and 3 for STAR 37), and the Stage 4 motor (0 if there is no Stage 4 in configuration, and 3 for STAR 37) respectively.

Credits: Orbital

The primary launch site used for Taurus is Site 576E on North Vandenberg Air Force Base (VAFB). Launches from North VAFB provide flight azimuths from 158 to 235 degrees, allowing payload injection on high inclination orbits (60 to 140 degrees).

For other mission profiles, there are a number of alternate sites that Taurus can launch from: South Vandenberg Air Force Base (VAFB), Cape Canaveral Air Force Station (CCAFS) Launch Complex 46, Wallops Flight Facility (WFF), and Reagan Test Site on the Kwajalein atoll in the western Pacific.

Taurus was designed to be launched from minimalist launch sites. The main requirement for the launch site is a 40×40 inch concrete pad that is able to support the weight of the launch vehicle.

For more information about the Taurus launch vehicle, you can visit the dedicated web page on Orbital’s website. There is also a Taurus User Guide available from Orbital. The guide is an exhaustive document, presenting the vehicle performance, the payload interfaces, an overview of the payload integration, among other things.

Credits: NASA/RASA

The Alpha Magnetic Spectrometer (AMS) is a high-energy particle detector. AMS will detect electrons, positrons, protons, antiprotons, and nuclei in cosmic radiation.

AMS is a cooperative project that involved more than 200 scientists from 31 institutions and 15 countries. The data gathered by AMS during its three-year mission will help scientists answer important questions about antimatter and invisible mass in the Universe. AMS could detect many types of particles predicted by theorists and determine their astrophysical sources.

AMS could reveal to scientists unusual astrophysical objects like antimatter galaxies, dark matter, strangelets, microquasars, and primordial black holes.

AMS actually refers to two particle experiments: AMS-01 and AMS-02. AMS-01 flew in low Earth orbit (LEO) with Space Shuttle Discovery STS-91 in June 1998. AMS-01 was an AMS prototype (a simplified version of the spectrometer) and was used to test particle physics technology in LEO. AMS-02 is the Alpha Magnetic Spectrometer designed to be mounted and operated on the ISS.

Credits: NASA

AMS-02 is a cube-shaped structure with a mass of 6,731 kg. The spectrometer consists of a huge superconducting magnet and six specialized detectors, and requires 2,000 watts of power.

The experiment has a 10Gb/sec internal data pipeline and will have a dedicated 2MB/sec connection to ground stations. AMS-02 will gather approximately 200 TB of scientific data during its mission. Four 750 MHz PowerPC computers running Linux will provide the computing power.

The spectrometer also contains two star tracker cameras, which detect the orientation in space, and a thermal control system that will control the temperature of the whole experiment. The thermal control system is quite complex. Heat is collected from the detectors and the magnet, and then pushed through conductors to the radiators mounted on the outside of the AMS and radiated into space.

AMS-02 has a little bit of history associated with it … due to the Space Shuttle accidents, which reduced the number of orbiters available, and the decision to retire the Space Shuttle fleet, AMS-02 faced cancellation (a long list of elements meant to be part of the ISS were cancelled for the same reasons). Because an additional shuttle flight was added to the launch manifest, most likely AMS-02 will make it to the space station.

The plan for AMS-02 is that it will be attached to the zenith side of the S3 section of the Integrated Truss Structure on the ISS. A Payload Attachment System will be used to keep the spectrometer in place on the truss segment.

Credits: NASA

According to the missions schedule, AMS-02 will be installed on ISS as part of the Space Shuttle Discovery STS-134 mission, together with the last ExPRESS Logistics Carrier (ELC-4), in late 2010.

STS-134 will be the last Space Shuttle flight before the deadline set to end Space Shuttle operations on September 30, 2010.

To make things more interesting (and Space Shuttle operations cheaper), it has been proposed that the last mission should end through a destructive re-entry. In this scenario, the reduced crew of three will remain on the space station and return to Earth onboard Soyuz spacecraft.

You can read more about AMS-02 on a dedicated web page at MIT. There is also a web page dedicated to AMS-02 at CERN.

Credits: JAXA

HTV stands for H-II Transfer Vehicle. HTV is an unmanned spacecraft designed and built in Japan. HTV is designed to deliver supplies to the International Space Station (ISS).

The typical mission for HTV starts at the Tanegashima Space Center (TKSC) near Tsukuba, in Japan.

A H-IIB launch vehicle will inject the HTV on a low Earth orbit (LEO). After the separation from the H-IIB second stage, the transfer vehicle is able to navigate independently.

It will take approximately three days for HTV to reach the proximity of the ISS. During this time, it will maintain contact with the Control Center at TKSC (designated as HTV-CC) through the Tracking and Data Relay Satellite System (TDRSS). TDRSS is a network of satellites that allow a spacecraft in LEO to maintain permanent contact with the control center on the ground. HTV will use GPS to position itself at 7 km behind the ISS.

At this point, the berthing phase of the mission starts. HTV will approach the ISS within 500 m and use the Rendezvous Sensor (RVS) to move closer to the ISS. Reflectors that are installed on Kibo will allow HTV to maintain a distance of 10 m below the ISS.

Credits: JAXA

HTV does not have the capability to dock on its own to the ISS (as opposed to the European ATV), so the Canadarm2 robotic arm will be used to grab the transfer vehicle and berth it to the nadir side of the Node 2 module.

While the HTV is berthed to the ISS, supplies from the HTV’s pressurized section are transferred to the space station by the crew, and waste will be loaded from the ISS.

The cargo from the un-pressurized section will be unloaded using the robotic arm and attached either to the Exposed Facility of the Japanese Experiment Module (JEM) or the ISS Mobile Base System.

The HTV mission will end in a similar way to the European ATV: a destructive re-entry above the Pacific Ocean.

Here is some more background information about the HTV. The spacecraft is a cylinder-shaped structure 10 m long and 4.4 m in diameter. It has a total mass of 10,500 kg, of which 6,000 kg is cargo (divided into 4,500 kg pressurized cargo and 1,500 kg un-pressurized cargo). HTV can carry 6,000 kg of waste during the re-entry.

HTV consists of four modules: the Pressurized Logistics Carrier (PLC), the Unpressurized Logistics Carrier (UPLC), the Avionics Module, and the Propulsion Module. The UPLC carries the Exposed Pallet (EP), which can accommodate unpressurized payloads.

Credits: JAXA

The PLC is equipped with a Common Berthing Mechanism (CBM). This will allow the crew present on the station to enter the module in order to unload the supplies and load waste material.

The EP carried by the UPLC can be either Type I or Type III Exposed Pallets. The Type I EPs will carry payloads for the Kibo’s Exposed Facility (EF), while the Type III EPs will be used to deliver the Orbital Replacement Units (ORUs) to the ISS.

The systems in the avionics module enable HTV to execute the autonomous flight to the space station. The module also contains communication and power systems. The thirty-two thrusters installed on the propulsion module provide HTV with the capability to execute orbital adjustments and control the attitude during the mission.

HTV will add to the existing fleet of transfer vehicles that includes the Russian Soyuz and Progress spacecraft, as well as the European ATV. The first HTV mission is scheduled for late 2009.

For more information about HTV, you can visit the H-II Transfer Vehicle page on the JAXA web site.

Credits: NASA/JPL

The Dawn spacecraft is currently performing the Mars flyby phase of its mission. The purpose of the Mars flyby is to alter the trajectory of the spacecraft in order to rendezvous with its first scientific target in the main asteroid belt.

The spacecraft will come within 549 km of the surface of Mars on February 17, 2009, at 4:28 PST.

The flyby is a gravity assist maneuver used in orbital mechanics to alter the trajectory of a spacecraft. The gravity assist is also known as a gravitational slingshot. The first ever gravity assist maneuver was performed by Mariner 10 in February 1974, and most of the interplanetary missions have made use of it since then.

The scientific objective of the Dawn mission is to answer important questions about the origin and the evolution of our solar system. The currently accepted theory about the formation of our solar system states that Jupiter’s gravity interfered with the accretion process, thereby preventing a planet from forming in the region between Jupiter and Mars. This led to the formation of the asteroid belt.

The asteroids chosen as scientific targets for the Dawn mission are Vesta and Ceres. Due to their size, they have survived the collisional phase, and it is believed that they have preserved the physical and chemical conditions of the early solar system. The asteroids have followed different evolutionary paths and have dissimilar characteristics, which makes them perfect research subjects.

Credits: NASA/JPL

The design of the Dawn spacecraft is based on Orbital’s STAR-2 series, and uses flight-proven components from other Orbital and JPL spacecraft: the propulsion system is based on the design used on Deep Space 1, the attitude control system used on Orbview, a hydrazine-based reaction control system used on the Indostar spacecraft, and command and data handling, as well as flight software, from the Orbview program.

The core structure of the spacecraft is a graphite composite cylinder, while the panels are aluminum core with aluminum/composite face sheets.

The central cylinder hosts the hydrazine and xenon tanks. The hydrazine tank can store 45 kg of fuel, while the xenon tank has a capacity of 450 kg.

The attitude control system (ACS) uses star trackers to estimate attitudes in cruise mode. A coarse Sun sensor (CSS) allows ACS to keep the solar panels normal to the Sun-spacecraft line. ACS also uses the hydrazine-based reaction control system for the control of attitude and for desaturation of the reaction wheels.

Credits: NASA/George Shelton

The solar panels are capable of producing more than 10 kW at 1 AU and 1 kW at 3 AU (on Ceres’ orbit).

The command and data handling system (CDHS) is based on a RAD6000 board running VxWorks. The software is written in C. There are 8GB available on the board as storage for engineering and scientific data.

The scientific payload consists of the Framing Camera (FC), the Gamma Ray and Neutron Detector (GRaND), and the visible and infrared (VIR) mapping spectrometer.

The FC will be used for determining the bulk density, the gravity field, for obtaining images of the surface, and for compiling topographic maps of Vesta and Ceres. In addition, the FC will capture images for optical navigation in the proximity of the asteroids. For reliability purposes, the payload includes two identical cameras that can run independently.

GRaND will serve for the determination of the elemental composition of the asteroids. GRaND is the result of the expertise accumulated during the Lunar Prospector and Mars Odyssey programs.

Credits: NASA/Jack Pfaller

VIR will help map the surface mineralogy of the asteroids. The instrument is a modified version of the visible and infrared spectrometer flying on the Rosetta mission.

The Dawn spacecraft uses ion propulsion to make its journey to Vesta and Ceres. Ion propulsion will also be used by Dawn during the low altitude flights over the asteroids.

While the fact that Dawn’s engines have a thrust of only 90 mN can hardly impress a reader, the important detail to mention when discussing propulsion systems is the specific impulse. Dawn’s engines have a specific impulse of 3100 s. For a chemical rocket, the specific impulse ranges from 250 s for solid rockets to 450 s for bipropellant liquid rockets. The only drawback (if this can be regarded as a drawback) is that the ion engines must be fired for much longer in order to achieve an equivalent trajectory.

With such high specific impulse engines, Dawn makes use of the fuel onboard in a very efficient way. The fuel used is xenon, a heavy noble gas placed in group 8A of the periodic table. The power produced by the large solar panels is used to ionize the fuel and then accelerate it with an electric field between two grids. In order to maintain a neutral plasma, electrons are injected into the beam after acceleration.

Credits: NASA/Amanda Diller

Dawn was launched from Cape Canaveral Air Force Station and injected on an interplanetary trajectory by a Delta II launch vehicle.

The main contributors to the Dawn mission are the University of California in Los Angeles (science lead, science operations, data products, archiving, and analysis), the Jet Propulsion Laboratory (project management, systems engineering, mission assurance, payload, navigation, mission operations, level zero data), and the Orbital Sciences Corporation (spacecraft design and fabrication, quality assurance, and payload integration).

The scientific payload was provided by the Los Alamos National Laboratory, the German Aerospace Center, the Max Planck Institute, and the Italian Aerospace Center. The Deep Space Network is responsible for data return from the spacecraft.

For more information about Dawn, you can visit the Dawn Mission Home Page on the JPL web site.

Credits: NASA

The Japanese Experiment Module (JEM) a.k.a. Kibo is the first contribution of the Japan Aerospace Exploration Agency (JAXA) to the International Space Station (ISS) program.

Kibo improves the research capabilities of the ISS by accommodating a maximum of four astronauts who can conduct scientific research activities and experiments in orbit.

JEM has six major components: the Pressurized Module (PM), the Exposed Facility (EF), the Experiment Logistics Module – Pressurized Section (ELM-PS), the Experiment Logistics Module – Exposed Section (ELM-ES), the Remote Manipulator System (JEMRMS), and the Inter-Orbit Communication System (ICS).

The PM is the largest component of JEM. It has a cylindrical shape, 4.4 m in diameter and 11.2 m in length. A total of twenty-three racks can be installed in the PM, six racks on each of the four walls, except for the zenith wall, which can accommodate a maximum of 5 racks. Some of the visible features are the airlock (which allows access to the EF), the two windows located above the airlock, the berthing mechanism for the EF (EFBM), an Active Common Berthing Mechanism (ACBM) on the zenith side for berthing the ELM-PS, and a Passive Common Berthing Mechanism (PCBM) used to connect with the port side ACBM of the Harmony module.

Credits: NASDA

The EF is a box-shaped structure, which is 5.0 m wide, has a length of 5.2 m, and a height of 3.8 m. The EF has 12 payload attachment locations. Each payload location can accommodate a science experiment that must be conducted in the exposed environment.

Kibo’s robotic arm (JEMRMS) is used for attaching and removing the payloads.

The ELM-PS is a cylindrical structure 4.4 m in diameter and 4.2 m in length. The ELM-PS contains a total of eight rack locations. ELM-PS can be used as storage space for experiments, samples, and spare items.

The ELM-ES provides storage space for up to three payloads. ELM-ES will be attached to the end of the EF. Besides the function of in-orbit exposed storage facility, the ELM-ES can also be used to return scientific payloads to Earth. The ELM-ES is a frame structure 4.9 m wide, with a length of 4.1 m, and a height of 2.2 m.

Credits: NASDA

The JEMRMS is a robotic manipulator system. JEMRMS will have two roles: supporting the experiments conducted on Kibo, and assisting with Kibo’s maintenance tasks.

A 10 m long Main Arm (MA), a 2.2 m long Small Fine Arm (SFA), and a robotic control workstation are the components of the robotic manipulator system.

The ICS has two subsystems: a Pressurized Module (ICS-PM) and an Exposed Facility (ICS-EF). The ICS-PM occupies a rack inside the PM, and provides command and data handling functions. The ICS-EF is basically the antenna used for communication.

Kibo is a large structure and more Space Shuttle missions are required to complete the deployment of all the components.

STS-123 Space Shuttle Endeavour delivered the ELM-PS component and ICS-PS to the ISS. JAXA astronaut Takao Doi was part of the STS-123 crew as mission specialist. During the mission, the ELM-PS was berthed to the zenith port of the Node 2 (Harmony) module. The ELM-PS carried the system racks and the experiment racks that are operated in the PM.

Credits: NASA

STS-124 Space Shuttle Discovery delivered the PM and the JEMRMS components to the ISS. The JAXA astronaut assigned to STS-124 as mission specialist was Akihiko Hoshide. STS-124 had to perform a number of operations in order to activate and assemble the pressurized components of JEM: installation and activation of PM, rack deployment, installation of JEMRMS, and the relocation of the ELM-PS from the zenith port of Node 2 to the zenith side of the PM.

The EF is the last major component of Kibo that has to be hauled to the ISS. The STS-127 mission will carry the EF, together with the ELM-ES and the ICS-EF components. The completion of Kibo will be done in two steps: the EF will be attached to the PM through the EFBM, and the ELM-ES will be attached to the EF as the last step. JAXA astronaut Koichi Wakata will be on board the ISS to supervise the operation as mission specialist.

The Japan Aerospace Exploration Agency has a web page dedicated to Kibo.

Credits: NASA

Kepler is the first NASA mission capable of finding terrestrial exo-planets. Of particular interest are the planets orbiting in the so-called habitable zone, where conditions are met so that liquid water can exist on the surface of the planet.

The observations made so far have brought clear evidence that planets orbiting around other stars are a common thing, rather than the exception to the rule. Due to the limitations of present technology, only gas giants, hot-super Earths in short period orbits, and ice giants have been discovered.

The Kepler mission, part of NASA’s Discovery Program, is designed to survey a portion of our region of the Milky Way. Kepler will survey a large number of stars, and explore the structure and diversity of many planetary systems.

The scientific objectives of the mission are very ambitious: determine the fraction of terrestrial planets in or near the habitable zone, determine the distribution of sizes and the orbits of exo-planets in the surveyed planetary systems, determine reflectivity, size, and density of short-period giant planets, estimate how many planets are in multiple-star systems, and determine the characteristics of the stars that have planets orbiting around them. Scientists hope to discover additional members of the planetary systems surveyed using other indirect techniques.

Credits: NASA/Ball Aerospace

The duration of the mission must be selected to allow the detection and confirm the periodic nature of the planet transits in or near the habitable zone. Due to the characteristics of orbits of such planets, a lifetime of three and a half years (as currently envisioned) would allow a four-transit detection of most orbits up to one year in length and a three-transit detection of orbits of length up to 1.75 years.

The mission lifetime will be extendible to at least six years. The extension will permit the detection of planets smaller than Earth with two-year orbits.

Kepler will be inserted in an Earth-trailing heliocentric orbit, then the spacecraft will slowly drift away from Earth. The selected orbit offers a very stable pointing attitude, and it avoids the high radiation dosage associated with an Earth orbit. However, Kepler will be exposed occasionally to solar flares.

The communication protocol with the spacecraft includes establishing contact twice a week for commanding, health, and status, and science data downlink contact once a month.

Credits: Jon Lomberg

There are two requirements that dictated the selection of the target field. The first requirement is the ability to monitor continuously the stars surveyed because transits last only a fraction of a day. This can be achieved by having the field of view out of the ecliptic plane, so the Sun will not interfere with the observations at any time during the year. The second requirement is to have the largest possible number of stars in the field of view.

To meet both requirements, a region in the Cygnus and Lyra constellations of our galaxy has been selected as the field of view.

Kepler will use the transit method for detecting exo-planets. The sensitivity of the photometer will allow the discovery of terrestrial exo-planets (planets comparable in size and composition to Earth that are orbiting other stars).

The transit occurs when a planet passes in front of its star as viewed by an observer. Depending on the size of the planet, the change in the brightness of the star has different amplitudes. Transits of terrestrial planets cause a change in the star’s brightness of about 1/10,000, and they last from two to sixteen hours.

Credits: NASA

Changes in star brightness that are produced by a planet transit must be periodic, and all transits produced by the same planet must cause the same variation of brightness and last the same amount of time.

Of course, the case when two or more planets are in transit at the same time must be considered, and this can make the detection method a little bit more complicated.

The method allows for the calculation of the orbit, the mass, and the characteristic temperature of the exo-planet. Once we know the characteristic temperature of an exo-planet, the question of whether or not the planet is habitable (by our standards) can be answered.

The Kepler instrument is a special telescope called photometer or light meter. The telescope has a very large field of view for an astronomical telescope, 105 square degrees. The primary mirror of the telescope is 0.95 m in diameter. The telescope needs a large field of view because it has to continuously monitor the brightness of more than 100,000 stars for the duration of the mission.

Credits: Ball Aerospace

The photometer is composed of one instrument, which is an array of charge-coupled devices (CCD), 42 in total. Each CCD is 50mm x 25mm and has 2200 x 1024 pixels. Data from the individual pixels that make up each star are recorded continuously and simultaneously.

The primary mirror of the photometer was coated with enhanced silver, which allows more light to reach the telescope’s detectors.

The spacecraft provides power, attitude control, and telemetry for the photometer. The mission requirements contributed to the simple design of the spacecraft. The only moving parts are the reaction wheels used to control the attitude of the spacecraft.

The launcher selected for the mission is Delta II. Delta II is a versatile launcher, and can be configured in two or three-stage vehicles in order to accommodate a variety of requirements.

Ball Aerospace is the prime contractor for the Kepler mission, building the photometer and the spacecraft, as well as managing the system integration and testing of the spacecraft. The Jet Propulsion Laboratory is managing mission development, while NASA Ames Research Center is responsible for ground system development, mission operations, and science data analysis.

Once the first observation results are downloaded from Kepler and made available to scientists, we will be able to place our solar system within the context of planetary systems in our galaxy.

The launch of Kepler is planned for March 5, 2009. For more information about the Kepler mission, you can visit the Kepler mission web page.