Mercury The closest Planet to the Sun

Here is a video that I put together than will provide more information about the planet Mercury.

A good resource for more information is the NASA Planetary Page that is found at

How Comets get their tail.

Comets start out as a dark object traveling through deep cold space. This shows how they grow a tail as they enter the warmer regions of space. A comets tail can stretch for many thousands of miles.

If you would like to read along, here is the text!

Comets are believed to have a solid core, and accumulate additional dust and ices on its surface as they travel deep into the Oort Cloud. As the comets elliptical orbit brings it back closer to the Sun, it approaches the distance of the asteroid belt, outside the orbit of Mars, where its ices begin to turn to gas, releasing hydrogen, carbon, oxygen, nitrogen, and other substances in the form of vapors and dust particles. They are carried away from the comet by the Solar wind, forming a tail. On its return path it cools and the tail goes away until the next trip.

Our Solar System

This animation shows our Solar System with the planets and dwarf planets in order orbiting the Sun.

If you would like to read along, here is the text!

Here we see our Sun orbited by the planets. The planets and dwarf planets are shown in order from the closest to the Sun, they are Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake and Eris.

The Outer Solar System is home to the Gass Giants, Jupiter and Saturn, Ice Giants Uranus and Neptune, Comets, Centaurs, and the Dwarf Planets Pluto, Haumea, Makemake and Eris. Saturn, Uranus and Neptune are encircled by planetary rings of dust, ices and other small objects.

The 4 terrestrial planets, Mercury, Venus, Earth and Mars, the asteroid belt and the Dwarf planet Ceres make up the Inner Solar System.

The Solar System consists of the Sun and its planetary system of eight planets, dwarf planets, their moons, and other non-stellar objects. It formed 4.6 billion years ago from the gravitational collapse of a giant molecular cloud.

The Inner Solar System

This animation shows the inner Solar System with the planets orbiting the Sun.

If you would like to read along, here is the text!

The inner Solar System is the region comprising the 4 terrestrial planets, and the asteroid belt that includes the Dwarf planet Ceres. The asteroid belt resides between the Orbits of Mars and Jupiter, it is thought to be remnants from the Solar System’s formation that failed to form a planet because of the gravitational interference of Jupiter.

The four inner planets have dense, rocky compositions, which form their crusts and mantles, and metals such as iron and nickel, which form their cores. The closest, smallest, and fastest planet, is Mercury. Next is Venus the hottest, similar in structure, and size to Earth, the planet we live on, is the third, Then we have, Mars, a cold desert world. It is half the diameter of Earth.

Three of the four inner planets, Venus, Earth and Mars, have atmospheres substantial enough to generate weather. All orbit the Sun in a counter clock wise direction, have impact craters and tectonic surface features such as rift valleys and volcanoes.

The Inner Planets

Take a look at the first four planets in our Solar System. This animation shows each planet zoom in and rotate then zoom out. The textures of the planets are maps made by NASA and found on the WEB.

If you would like to read along, here is the text!
Mercury Orbits, the Sun in 88 days, it’s the closest planet to the Sun, fastest, and the smallest planet in the Solar System, .055 the mass of Earth. Its only known geological features besides impact craters are lobed ridges, produced by a period of contraction. The almost negligible atmosphere consists of atoms blasted off its surface by the solar wind.

Venus orbits, the Sun in 224.70 Earth days, it’s close in size to Earth, has a rocky mantle around an iron core, substantial atmosphere and evidence of internal geological activity. However, its atmosphere is ninety times as dense. The hottest planet, with surface temperatures over 400 °C, due to the greenhouse gases in the atmosphere.

Earth, the largest and densest of the inner planets, the only one to have current geological activity, and the only place where life is known to exist. Orbits the Sun in 365.26 days. Its liquid hydrosphere is unique among the terrestrial planets, and the only planet where plate tectonics has been observed. The atmosphere has 21% free oxygen.

Mars is half the size of Earth. Orbits the Sun in 686.98 Earth days. It’s atmosphere is .6% of that of Earth, made of Nitrogen, Argon, and mostly Carbon Dioxide. The surface has a vast number of volcanoes such as Olympus Mons, rift valleys such as Valleys Marineris . It’s red color comes from iron oxide, rust in its soil.

Lunar Orbit of the Earth

This demonstrates the orbit of the Moon around the Earth and is a good companion to the earlier post Tilt in Earths axis. NASA defines the period of the Moon’s orbit to be one complete orbit in 27.3215 days that translates to 27 days, 7 hours, and 43 minutes. The cycles or phases of the Moon are due to it’s orbit around the Earth and the angle that the light from the Sun illuminates the Moon. As demonstrated in this animation as the Moon progresses through it’s orbit it will cycle from full illumination (the Full Moon) to total darkness (called new Moon) and back to full illumination as viewed on the earth. The tilt in the Moons axis is 1.54 degrees and the orbit has a 5.14 degree inclination to the Sun line, when added together the resulting tilt in axis is a total of 6.68 degrees.

This animation shows the spin of the Earth and movement of the Moon relative to the Moons orbit period. You can also see how the the phase of the Moon is based on it’s location in the orbit.

ILM Antenna being installed.

The Improved Limited Motion (ILM) Antenna installation started with site location and preparations.  Due to wind loading, weight requirements and stress analysis these antennas must be secured to a solid base. In this case the antenna was being installed on the roof of a new 2 floor addition to the facility. Extensive engineering and analysis was done during the design of this addition to insure that the antenna could be added safely.

Four pads were prepared for the installation to secure the antenna structures to the roof. The mounting bolts were secured in high strength concrete based on the antenna manufactures specification and the structural analysis.

ILM Antenna location for installation

When the antenna arrived, the install team unpacked and inventoried the shipment, placing the components in the defined assembly area. The assembly started by placing the hub on a stable fixture. The back frame that holds the dish panels in place was assembled. Each support strut and mounting bracket had to be aligned and torqued down in place to ensure the stability of the completed surface. The panels were installed and aligned with openings left to accommodate access and simplify attachment of the completed dish structure to the pedestal.

A crane was used to lifted the pedestal of the antenna into position on the roof  where it was aligned and secured. With the pedestal securely in place the crane lifted the dish and it was guided into place.

After verifying the alignment of the panels, the support structure and sub-reflector assembly could be installed. Final panels were then installed in place to complete the dish.

The antenna control interface, motors, RF equipment, cabling and waveguide were installed. Mechanical and communications testing followed to commission the antenna for service.

The completed antenna shown in this final picture.  Exterior panels were added to inclose the support structure of the antenna. This was part of a de-icing system that used propane heaters to warm the dish surface and feed assembly preventing snow or ice from  accumulation during the winter season.  As with all antennas of this type lightning rods were installed and grounded to protect against damage from lightning strikes.

TT&C Ground Station

Back in 1980 after leaving the Army, I was hired to work for SBS as a Satellite Controller and ground station technician at their Satellite Control Center (SCC).  The Clarksburg Telemetry, Tracking and Command (TT&C) ground station in Maryland was nearing completion and was under acceptance testing in preparation for the first launch of a SBS satellite. Over 14 years of operation the station facilities grew to include added functionality, Carrier System Monitor (CSM) area, Central Reference Station (CRS),  Video Support Center (VSC) for uplink monitoring and assistance and finely a Launch Control Facility. The station power was supported by an uninterpretable power system including 500 KW diesel and turbine generators,  battery backup and an automated transfer system to switch from commercial power to the backup systems. Office space was available for management, the engineering staff and a facilities engineer who maintain the heating, air conditioning and humidity control systems.  Each shift was staffed to support 24 hour operations of all of these functional areas and also maintain or repair the equipment.

SBS TT&C ground station early 80's

This picture shows the 3 NEC 7.8 meter Ku-Band limited motion antennas we used for control of the SBS satellites. Also shown is a mobile ground station parked between 2 of the fixed antennas that we used for video demonstrations and remote onsite testing. The NEC antennas moved in the X and Y axises using jack screws driven by electric motors.  Once the antenna was pointed at the satellite it was capable of tracking using a modified program track system. The antenna drive speed was 0.01 degree per second, and the range of movement was limited to a section of the satellite ark assigned to the SBS satellites for on orbit operations. These antennas were linear polarized and the feed assembly  could be rotated for horizontal or vertical polarization. Electric heating elements were imbedded in the individual panels of the dish and are used to prevent accumulation of snow or ice on the dish surface. During on station operations of the satellites, data is collected and process as telemetry, time stamped X & Y angle data measurements are taken to process tracking and used in orbit determination,  range tones are transmitted and received , and commands are sent to the satellite.

The SCC section of the Operations area shows the racks to the left that held the HP 1000 E series mainframe computers used for satellite and ground systems  command,  control, and data processing. The baseband processing, voice communications network and time translation  equipment was located in the center. With the modems and interfaces to dedicated data and voice lines to the right.  Status changes and alarm conditions were sent to the event status printers located next to the two computer control terminals.

SBS SCC computers and Baseband racks

(This was state of the art in high tech at the time).  This room had raised floors to allow cabling and airflow to cool the racks of equipment. The three cabinets to the right in the picture are an EdPac system used to control humidity and maintain the rack temperature between 65 and 68 degrees to optimize equipment performance and eliminate the potential of static shocks. For fire protection the room was designed with a halon system that would seal the room, release the halon into the room to extinguish the fire and then evacuate any smoke and/or halon gas from the room in less than 2 minutes.

Satellite control and monitoring was preformed at this console that accommodated 2 flight controllers and a operations engineer. The monitors on top of the console provided a visual status of the RF equipment for each antenna, the transmit and receive path configurations, the IF equipment used in the paths in addition to computer status alarms.

The right half of the console was setup for commanding operations and the left side to allowed other satellites to be monitored simultaneously. Satellite simulators were used for launch preparation and to provide training of new engineers and controllers without interference with ongoing operations.

Pre-command checks

The 4 racks seen in the background of this picture contain the NEC RF equipment. Frequency conversion was accomplished using up and down converters that had a shared synthesizer to simplified link frequency selection. Each link had an attenuator to set it’s operating  level and provide an adjustment to raise or lower the output as needed. The transmit rack housed the IPA and HPA’s used to achieve the required transmit output power levels needed to meet the required link margins.

In the next picture the racks to the left support IF conversion and Antenna control equipment. The IF section has FM and Phase modulators for the transmit side and receivers with demodulators on the receive side.  IF input and output switch matrix hardware allowed computer or manual configuration of the up and down links at the 70MHz level.  The antenna control panels used by the operations team to manually point the antenna, change polarization from Horizontal to Vertical with minor angle adjustments, select program, modified program or step tracking, in addition to operations of the de-icing system. SCC expanded to full capacity

The Carrier System Monitor (CSM) equipment was initially installed by COMSAT General Corp.

CSM initial installation nearing completion

This system was used to monitor the traffic over the full 500 MHz frequency bandwidth of the satellite.  It contained all test equipment required to analyzed each link and track transmitted power, frequency, bandwidth, type of modulation and data error rates for each user on the satellite. We preformed acceptance testing on each of the 3 systems.

The fully operational system was optimized so one person could operate all 3 systems, monitoring 3 satellites at the same time. The CSM provided the capability to monitor traffic 24 hours a day and also supported network activation and customer network support.  These activities included daily carrier/traffic analysis, printouts used in network monitoring, status reporting, trending and to support information requested by the customer billing office.

CSM in full operations

The racks in the back to the left in the picture above (not completely shown) is the Video Support Center area.  As SBS started to lease out more space on the satellite for full time and occasional use video transmission services, 4 racks of video support equipment were added. Color-bar generators were used to provide test patterns along with all video test equipment needed to test the quality of the video up and down links.  As the satellite links started to be encrypted VideoCypher units were also installed and maintained as part of our support.

As an upgrade RF equipment installation started on the third antenna after the second satellite was launched.

Installation of LM-3 RF racks.

The Central Reference Station was installed to provide timing for networks. Using a ultra-stable timing source, the system would transmit a TDMA carrier into each of the 10 channels of the satellite providing a common reference. This would allow a more dynamic and flexible network configuration so any station could transmit on only one channel while receiving on more than one channel using this reference signal.

Additional RF racks being completed for the CRS

In preparation for our third satellite additional RF equipment and a fourth antenna was installed for backup.

Four operational LM Antennas

In the mid 80′s an addition was built to expand the SCC to support up to 6 satellites and preform Launch and checkout operations. This added 2 floors with a new SCC on the first floor, the Mission Control Center (MCC) launch operations facility on the second floor and 2 Improved Limited Motion (ILM’s) Azimuth – Elevation tracking Antennas made by TIW.

Expantion of building completed.

The new SCC had areas supporting control, new HP A900 computers and processing equipment, data analysis, and offices for the Operations manager and engineers.

New Satellite Control console

The new console used new HP 100 terminals equipped with touchscreen technology. Security monitors and remote control cameras were installed to view the equipment and the facility grounds.

The computer system controlled graphics generators connected to a video switch for easy switching of telemetry displays, security cameras, graphs, and video feeds. New Cisco switches and roughers were installed along with dial back modems for network configuration and remote access.

The offices had access to monitors and the video switch to monitor data and operations.

The Mission directors console in the MCC had monitors that were connected to a video switch used to select displays of satellite telemetry, plots, launch site video feeds, or signal strength test equipment. The voice network could access any of 8 channels ranging from remote tracking stations to the launch site in addition to telephone lines and operations networks. There were corded handsets and headsets available for each work area.

The engineering support consoles, had the same features for each subsystem engineer.

For support of additional backup power requirements a new 500 KW turbine generator  was added during the expansion.

This TT&C station was used by SBS, and in 1985 became part of MCI.  By 1990 this facility was sold to COMSAT.  COMSAT moved their control center to Clarksburg and integrated both operations to control 8 satellites form this site. Eventually COMSAT converted the station into a Tele-port as the satellites reached the end of their operational life and now it is owned and operated by Lockheed .

Solar Array Deployment

At launch the satellite solar panels are folded against the body of the satellite (stowed configuration) to minimize space and allow the satellite to fit into the faring of the launch vehicle. Once the satellite has been placed into Geosynchronous orbit the ACS system is activated to point the proper axis of the satellite at the earth. This process is called ACS initialization and Earth capture activation. During this period the satellite is being powered by the batteries. Once the Earth sensors are activated and the ACS system is locked onto the Earth, the solar panel release mechanization can be actuated to allow the arrays to unfold and lock into a deployed position. With the arrays deployed the solar array drive system is activated and commanded to track the Sun. The following animation shows the release of the North panel, then the South panel, followed by the positioning of the panels to point directly at the sun.

This would be the worst case condition where the arrays are pointed 180 degrees away from the Sun, the arrays are typically deployed at a time of day that allows them to be pointed at the Sun so they only require minor pointing changes to peak their power output. With a 180 degree pointing offset as shown the arrays would be commanded to move in opposite directions (one clockwise and the other counter clockwise) at the same time. From the ACS control standpoint the torques on the body of the satellite would relatively cancel and minimize the error correction required by the ACS system. After the the arrays are peaked on the Sun the Solar array drive system is commanded to normal tracking mode to maintain this pointing through a full 360 degrees rotation over the course of the day. As soon as there is adequate power being generated from the arrays, the power load will transition from battery to array power and battery charging can be started.

Solar Array Drive

Solar Array Drive (SAD) refers to the system that positions the solar panels on the satellite to efficiently convert s the sun light into electrical energy. This system is comprised of the Solar Array Drive Assembly (SADA) and the Solar Array Drive Electronics (SADE).

The SADA includes the stepper motor, drive gear assembly, Barring And Power Transfer Assembly (BAPTA) and the mounting hardware required to mount the solar panel to the body of the satellite. The solar panel is mounted to the SADA and allowed to move by means of the barrings in the BAPTA. It also includes a slip ring assembly used to transfer the power generated by the solar panel to the EPS bus. The drive gear assembly is installed to smooth the step movement of the motor and provide a steady constant travel through 360 degrees of rotation. Stepper motors are known for their ability to provide high torque and controlled movement, this makes them ideal for this application. Rather than mounting two motors in the assembly, to increase the reliability these stepper motors are designed with redundant coils, this effectively reduces weight and provides improved redundancy.

Each SADA is controlled by independent Solar Array Drive Electronics (SADE) unit that provides the interface between it and the EPS subsystem or flight computer. It is comprised of all of the circuitry required to generate and shape the pulses needed to drive the stepper motors. Telemetry monitoring sensors collect data such as current, temperature, position, speed, rotational direction of travel, step counts, and status indicating movement or stopped for the SADA.

In operation the rotation of the solar panel is started when the SADE is enabled and step pulses are received, movement stops between steps or when it has been disabled. Control of the direction of travel, can be commanded to rotate in either forward or reverse direction to allow for pointing position optimization. The SADE is normally configured to output a consistent train of pulses at the required intervals to maintain movement through the 360 degree rotation called Normal Mode. With the panel rotating less than 15 degrees each hour it is easily commanded at less than 5 times a second allowing for rest intervals between movement. Speed and torque can be adjusted by increasing or decreasing the rate of pulses per second (pps) sent to the motor. If the motor is normally driven at 5 pps then driving it at 25 pps will increase the speed by a factor of 5. This system is typically design for the solar panel to complete a full 360 degree rotation in less than 15 minutes at the highest pps command rate. When commanding the movement of the SADA, commands are processed by the SADE, stored and then pulses are sent at a 5 pps or 25 pps rate until the complete commanded step count is reached. At completion the SADE must be commanded back to the Normal Mode or transitions back automatically.

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Shining light on satellites and how they operate. Drawing from over 30 years of knowledge and experience in all phases of the life of a satellite from concept, to operations, and through end of life. You will find short topics intended to give you an understanding of how they work, the general concepts, and principals used along with information on ground systems. There is also a section dedicated to topics that can be used as basic concept training along with links to animations and 3D models I have created.