LM3909 – An IC Just to Flash an LED

So during my placement year I was getting really into old electronics, and old IC’s, especially those no longer in production. We were also on a project where we were trying to design a circuit that would flash an LED for a short period of time from the charge on a small super capacitor. The big issue we had was how to minimise current flow, and power an LED at really low voltages, less than 2V. This on the face of it seems like a simple problem, until you start to think about it.

Million Mile Light
Products like the Million Mile Light, a flashing low powered, high brightness LED indicator need to flash for long periods of time on very little charge, much like the problem I faced. Credit: Million Mile Light

There are two go to ways that most engineers would go with to make a flashing LED with a constant flash rate. First is to use a small microcontroller, such as an ATTiny, or a Pic12F series, and use software to flash the LED. This seems good on the surface (and it is what we used in the end product) but it has a big drawback, it can only output a voltage less than the power rail. some versions of the PIC12LF’s can function down to 1.8V, perfect for our power supply needs, but LED’s need upwards of 2.7V (usually) before they start to light, so although our micro will work the LED wont. The second go to way to make an LED flash would be to use the classic 555 timer, one of the most manufactured chips of all time. There is a good reason it is famous, it is extremely versatile. You can decide the frequency based purely on the capacitor and resistor choices. We still have a similar drawback though, a 555 timer needs at least 4.5v as a power supply. So with our potential sub 2V power supply, neither the IC or the LED will turn on. That is one way to conserve energy!

A cut out from the datasheet, with a basic view of the circuit inside the IC, which I will go through in another post, and a pinout diagram, very useful for prototyping. Credit: National Semiconductor.

This is where the LM3909 came in to play. You have to remember that this chip was developed prior to 1995 (so it is older than me) when the electronics market was very different. Battery technology was not the same, and nowhere near as cheap. It was much more common for people to want to use off the shelf single use batteries such as AA, C and D batteries, or even coin cells in most projects. If you wanted something with a little flashing light on it there were plenty of applications for it. There are buoys in the ocean, store signs and displays, and Christmas lights, all of which would benefit from minimising weight of batteries, but lasting for serious amounts of time. Just as a reference, you could get to 4.5V (to power a 555) by using 3 AA batteries, but the voltage across them would soon dip below this, so you would need at least 4 in most applications. 4 AA batteries take up a lot of space, and weight, not great for many of these applications. Plus most of the chips we have discussed use a fair amount of power, the 555 uses at least 3mA while running, not including the dissipation in the resistors, and all of the power charging the capacitor wasted.

1.5v schematic
A snippet of the datasheet, showing the simplest connection diagram, and a graph of typical current consumption with relation to the battery voltage. It also has a great table describing how long standard batteries tend to last in this configuration, up to 2 years! Credit: National Semiconductor.

So how does the LM3909 solve these issues? well it makes use of a clever concept similar to the 555 of charging up a capacitor. The difference is that the 3909 uses that charge in the capacitor to flash the LED. Although it is slightly more complex than the below schematic, you can think of it as there being a switch inside that oscillates between two states. We will go through how it actually works in a future post. To start with the capacitor is in series with the battery, and in parallel with the LED. The LED wont light, but the capacitor charges up to near the power supply voltage. Once charged, the switch inside flips, and now the power supply, charged capacitor, and LED are in series with each other. To the LED it now sees the capacitor (charged to 1.5V) plus the 1.5V power supply, equivilent to 3V, more than the forward voltage it needs to turn on. As there is a very small resistance, the LED will be on as long as the capacitor has some charge, which isn’t very long as it will discharge fairly quickly. This is the “flash”, as once the cap is discharged the LED will turn off, and the switch will flip back. The capacitor starts charging again, and the whole process restarts. This goes on for as long as the battery has power to give.

Rob Paisley
A great description of the basic principle of how the LM3909 works, charging the capacitor up, and then releasing all that energy through the LED, with increased voltage. Credit: Rob Paisley.

A couple of points to note, the timing and the brightness of the flashing is based upon the capacitor you use, which is quite clever. There are two settings, depending in the pin you put the capacitor in will also double (or halve) the time the cap will take to charge. This means slower flashing, but longer lifetime. Having a smaller capacitor will mean faster, but less bright flashing, and a bigger cap will therefore be slower and much brighter flashing. The design of the chip also means that only two external components are needed for it to work, a capacitor and the LED, compared to the many resistors and extra cap needed on things like a 555 timer. The fact it can use less than 1.5V power source means we can use a single AA battery to power this device, and according to the data sheet it can last up to 6 months on one battery! I have one on my desk that has lasted longer than this.

my LM3909 circuit
My version of this circuit fit into a AA battery box, with it being powered by a single AA battery. It has a switch meaning I can turn it on and off. Poundland LED lights are a good source of these!

All in all I can see why National Semiconductor decided to make this chip, it filled a gap, and was used widely for a long time. Developments in battery technology, and more complex designs needed for the applications this was for has meant that they no longer make the LM3909, but they are still available on Ebay and some Chinese manufactures make them. There is also a design out there to make a discrete version of the LM3909, and I may try that for a future post, as it looks interesting.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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Delta 4 Medium Makes Penultimate Launch

John Kraus photos
A great image taken by John Kraus of the Delta 4’s main booster and four smaller boosters, and the awesome power they produce. Visit his patreon to find more! Credit: John Kraus

Just after midnight, 00:23 UTC on March 16th 2019, a Delta 4 medium rocket placed a US military network relay satellite into orbit. Launching from Space Launch Complex 37B at Cape Canaveral AFB in Florida, the 66 meter tall Delta 4 is nearing retirement, with this being its second to last launch. After several technical issues, the ground teams eventually got the rocket and the satellite tracking network functioning correctly. The hydrogen fueled RS-68A main engine ignited moments before liftoff for 5 seconds before the hold down bolts released at T-0, firing away with 1.8 million pounds of thrust. This mission has extended ULA’s streak of successful missions to 133 since its inception in 2006.

Marcus Cote
Maybe the photo of the night by Marcus Cote, showing the huge exhaust plume created by the Delta 4 in 5, 4 configuration. Credit: Marcus Cote
marcus cote
A great time lapse of the Delta 4 launching WGS10 satellite into a geostationary orbit. Credit: Marcus Cote.

The rocket veered towards an easterly direction over the Atlantic Ocean, aiming to place the communications satellite to its final operating position 36,000 km (22,000 miles) above the equator in geostationary orbit. The solid rocket boosters burned out and were jettisoned in pairs roughly 1 minute and 40 seconds into flight. The main engine continued to fly on until 4 minutes in when the first stage was cut off, and then released shortly after. The first stage then fell back to Earth into the Atlantic Ocean. The upper stage was powered by a RL10B-2 engine, made by Aerojet Rocketdyne, the same manufacturers of the main engine. The upper stage engine ignited twice to push the satellite into an elliptical transfer orbit. The satellite separated from the second stage at T+36 minutes 50 seconds.

An image showing the scary power of the rocket boosters at liftoff, the rocket firing 1.8 million pounds of thrust into the ground trying to escape the Earth. Credit: ULA.

On board was the WGS 10 military communications satellite. It is a 6000kg (13,200 lb) broadband satellite, that is joining nine others that have been slowly placed in orbit since 2007. The idea is to form a globe spanning network that can relay video, data and other useful information between the battlefield and the headquarters, wherever they may be. The WGS fleet transmits both classified and unclassified information, and supports the US and its allies. On board is a digital channelizer that allows the satellite to relay signals using high data-rate X-band and Ka-band frequencies during its 14 year expected life. All of the WGS satellites were launched on ULA rockets, with the first two on Atlas V’s and all the rest on Delta 4’s. This mission had an estimated price tag of $400 million.

Glen Davis
An almost artistic image of the Delta 4 medium launching. Heavily edited, but still capturing that raw power. Credit: Glen Davis

Marking the second to last flight of the Delta 4 Medium variant rocket, it is noticeable as only having a single first stage core, whereas the Delta 4 Heavy has three. ULA are retiring certain areas of their launch family as they plan to debut the new Vulcan booster soon which will apparently be cheaper than their current offering. The decision to halt selling of the Delta 4 medium flight was made in 2014, but this and the next launch were already on the books at that time. The Delta 4 medium is apparently more expensive than the Atlas V launcher, but with a similar launch capability, leading to the reason for retirement. ULA described it as it being cheaper to run a few launchers more frequently than many launchers sporadically. The bigger Delta 4 heavy will continue to launch heavier payloads well into the mid 2020’s. Another reason for keeping the Delta 4 Medium was to allow the US military to have two choices to launch their payloads, that and the Atlas V. Now that the Falcon 9 is cleared to fly military satellites there is less need for the Delta variant.

marcus cote
The Delta 4 sitting on the pad, ready to launch the WGS10 satellite. Taken close up by Marcus cote the day before when setting up the remote cameras for the launch. Credit: Marcus Cote.
mike seely
A behind the scenes photo of setting up cameras before the launch. Credit: Mike Seeley.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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The Crew Dragon Flies

Crew Demo landing

This weekend a very important event happened, something many rocket enthusiasts have been waiting for. The first capsule designed to hold commercial crew was launched by SpaceX. A successful launch, the Falcon 9 carrying the first crew Dragon lifted off from pad 39A at the Kennedy Space Centre, Cape Canaveral, FL on the 2nd of March 2019 at 07:49 UTC. This was the first orbital test of the Dragon capsule, and although it was unmanned, it did hold a dummy test astronaut nicknamed Ripley, after the heroine from Alien.

loading the rocket
The modified Falcon 9 being rolled out towards the launch pad on the specially designed trailer. Credit: SpaceX
Crew Dragon
A close up side on view of the Crew Dragon while it it waiting to be loaded. Credit: SpaceX

The capsule was launched on top of the 70m tall Falcon 9 that had minor changes to work with NASA’s strict requirements for commercial crew. Trailing off in a north easterly direction, the Dragon capsule sailed on a 27 hour autonomous route towards the International Space Station. The capsule itself is 16ft tall, and 13ft in diameter, and is designed to be able to hold 7 people in relative comfort (compared to the previous equivalents). This capsule sits on top of a trunk that could contain some cargo on future trips. The capsule is 12ft tall, 12ft in diameter, and coated in solar arrays. The cargo section is not designed to survive a journey back to Earth, with the heat shield and thermal protection system being on the capsule itself.

John Kraus Photos
A great long exposure shot of the Crew Demo launching, taken from Merritt Island. FL. Credit: John Kraus Photography. Click on the photo and buy one of his rocket prints!

The first stage of the Falcon 9 powered through the thick lower atmosphere for about 2 and a half minutes before shutting down and separating. The booster B1051.1 was brand new, performing landing burns on its way back through the atmosphere to come back and land successfully on the autonomous drone ship “Of Course I Still Love You”. The landing was particularly rough with choppy seas out in the Atlantic that day. The booster did not manage to hit right on the X on the pad, but was still stood up when it returned to port Canaveral. This was a big moment as it is now the 35th successful booster recovery. Just a minute after the first stage landed the second stage engine cut-off. A few moments later the Crew Dragon was released from the second stage to begin the 27 hour journey to the ISS.

A landscape view of the launchpad 39A at Cape Canaveral, with the first commercial crew mission on board the Falcon 9. Credit: Marcus Cote Photography. Click the image and go buy one of his prints!

The 400lb capsule glided to an automated docking early on Sunday morning, completing one of the major milestones of the mission. Aided by a laser rangefinder and a thermal camera the Dragon capsule approached the space station and linked with the docking port on the forward end of the complex at 10:51 UTC. This is now the first privately owned human rated spaceship to reach the ISS. The link up happened at over 400km over the northern end of New Zealand during what is known as orbital night time. The capsule first held back at around 60 m from the station, testing radio links. When given the go ahead it then moved towards the ISS at 10cm per second or 0.2mph. The capsule actually arrived 9 minutes ahead of schedule when the latches engaged to create a connection with the International docking adapter.

Crew Dragon
The Crew Dragon moving slowly towards the ISS. Credit: NASA

The station docking adaptor was installed over the old space shuttle docking port, at the forward end of the Harmony module. The arrival marks the first time a visiting spaceship has docked there since the last flight of the shuttle Atlantis in 2011. Once docked 12 hooks closed to forma firm mechanical connection, and then two umbilical lines were attached by robotic arms to allow the stations electrical system to power the Dragon module during the stay. After a number of checks, Saint-Jacques opened the crew Dragons hatch, becoming the first person to board the ship. The crew wore face masks when entering the Dragon, as they would with any other visiting spacecraft, for precaution. Once the capsule was given the all clear the crew removed their masks and unloaded the 100 lb of cargo stowed under the seats. On board the Dragon was a small stuffed toy in the shape of Earth, made by Celestial Buddies. NASA astronaut Anne McClain quickly picked it up and made a video with it. Celestial buddies were unaware that they would have one of their toys would be going on a mission, and they are therefore sold out for now, but they have some great other toys on offer instead.

Crew Dragon
A closer view of the Crew Dragon, just moments bore docking. Credit: NASA
long exposure of the Falcon 9
A 277 second exposure of the Falcon 9 launching from LC-39A, so long that it shows the separation of the first stage. Credit: Mike Seeley.

The Crew Dragon will depart the space station early on Friday at 07:31 UTC, followed by a de-orbit burn at 12:50 UTC. The spacecraft jettisons the unpressurised trunk section, with the solar panels and radiator, what will burn up in the atmosphere. The heat shield on the Crew dragon will then protect it as it comes into the atmosphere from a northwest to southeast direction. Aiming for a splashdown under the four parachutes somewhere in the Atlantic Ocean, east of Cape Canaveral at 13:45 UTC. The next big test for the Crew Dragon will be a launch where the launch escape system is tested. Designed to push the capsule away from the rocket if there is a major failure, that launch will be in late June of 2019 if all goes well. The first crewed mission is planned for July this year.

A great image turned into a poster from the rocket launch, with an emotive quote by Elon Musk. Credit: Erik Kuna.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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The First Launch of a Commercial Lunar Lander

Marcus Cote Photo
A Falcon 9 lights up the sky above the Space Coast for the first time in 2019. Here’s a long exposure from 321 Boat Club in Melbourne, Florida. Credit: @marcuscotephoto

At 01:45 UTC on February the 22nd 2019 an already flown Falcon 9 was the first SpaceX rocket flown from the Cape in 2019. Launching from SLC-40 in Cape Canaveral, FL, the 70 metre high rocket flew three satellites into space. On board was an Indonesian communications satellite, a privately funded Israeli moon lander and an experimental space surveillance satellite for the US Air Force. The Falcon 9 first stage booster successfully landed back on Earth for a third time, landing on the autonomous drone ship “Of Course I Still Love You”.

SpaceX launch
A shot of the Falcon 9 launching from SLC-40 at Cape Canaveral with 3 satellites on board. Credit: SpaceX.

The Israeli moon lander is the first of its kind, attempting to be the first privately funded mission to the Moon. It was also the first to separate from the rocket at 33 minutes after liftoff. Within minutes of separation the spacecraft opened its four landing legs and radioed ground control with a status report. At 585 kg at launch it is not especially heavy for a spacecraft, and not the heaviest on board, but without fuel it would only be 150 kg. It is roughly 2m in diameter and 1.5 m tall with the landing legs extended. It is named Beresheet after the Hebrew title of the biblical book of Genesis. After several orbits of the Earth the spacecraft will begin to slowly raise its orbit with the on board thrusters. The process will take roughly 7 weeks to reach the Moon’s area of gravitational influence. At that point the spacecraft will perform manoeuvres to be captured into a lunar orbit, staying there for between two weeks and a month. When in the correct orbit, it will attempt a soft landing on the surface, aiming at the northern end of Mare Serenitatis. The landing zone is a circle of about 15 km.

SpaceIL co-founders Kfir Damari, Yonatan Winetraub and Yariv Bash insert a time capsule on the Beresheet spacecraft. Credit: SpaceIL
spacex launch
Great view of the 9 engined, 70m rocket launching from the Cape in late February. Credit: SpaceX

The aim of the Moon lander, beyond being the first commercial lander, is to measure the Moon’s local magnetic field to help understand how it formed in the early solar system. To do this it has an on board magnetometer, made by the Weizmann Institute of Science. It also has a laser retroreflector array payload provided by NASA Goddard Space Flight Center. This is a device that will reflect a laser back the direction that it came from. The Apollo astronauts installed a similar device that is still used today to measure the distance the Moon is from Earth at any one time. You do need a very powerful laser to achieve this though. With minimal science instruments the spacecraft is not designed to last long on the surface. It has no thermal control so is expected to quickly overheat when functioning. It therefore has an expected life of just two days after landing on the surface. The craft also has a digital time capsule that contains over 30 million pages of data, including a full copy of the Bible, English-language Wikipedia, many children’s drawings, memories of a Holocaust survivor, Israel’s national anthem, the Israeli flag and a copy of the Israeli Declaration of Independence.

rocket landing
The Falcon 9 rocket’s first stage lands on SpaceX’s drone ship “Of Course I Still Love You.” Credit: SpaceX

Made as a competitor for the Google Lunar X prize, Beresheet is made by SpaceIL. They are a non-profit, and have reportedly produced the mission for less than $100 million, which is extraordinarily cheap for this kind of mission. This is going to be the first private interplanetary mission that’s going to go to the moon,” said Yonatan Winetraub, a co-founder of SpaceIL, which had its origin in a brainstorming meeting in a Tel Aviv bar. “This is a big milestone. This is going to be the first time that it’s not going to be a superpower that’s going to go to the moon. This is a huge step for Israel.

“Until today, three superpowers have soft landed on the moon — the United States, the Soviet Union and recently, China,” . “And (we) thought it’s about time for a change. We want to get little Israel all the way to the moon. This is the purpose of SpaceIL.”

Winetraub, in a news conference
long exposure launch
Long exposure of the launch from across the water. Credit: SpaceX

The Indonesian Nusantara Satu communications satellite was by far the heaviest payload on board at 4,100 kg, deployed 44 minutes into flight. Formerly known as PSN-6, Nusantara Satu is a high throughput satellite that will provide voice and data communications as well as broadband internet throughout the Indonesian archipelago and South East Asia. Built by SSL for PT Pasifik Satelit Nusantara, it was the first private telecommunications company in Indonesia. The cost of the project is estimated at $230 million. The mission uses solar electric ion thrusters to get to the correct orbit, but will employ conventional chemical thrusters to stay in that orbit. It is expected to last at least 15 years.

Nusantara Satu
The Nusantara Satu spacecraft, topped with the Beresheet lunar lander and the U.S. Air Force’s S5 space situational awareness satellite, is pictured before encapsulation inside the Falcon 9 rocket’s payload fairing at Cape Canaveral. Credit: SSL

The other secondary payload on the Falcon 9 was an experimental Air Force satellite intended to test space situational awareness technologies. The flight was brokered by Spaceflight, a Seattle based company that finds rideshare launch services. The S5 satellite was made for the Air Force Research Laboratory (AFRL). Although the mission has had very little information released about it there has been some. Blue Canyon Technologies announced in September 2017 that it won a contract from AFRL to build two small satellites to operate in GEO. One was identified as S5, a 60 kg satellite using a payload provided by Applied Defence Solutions. The illustrations released show an optics system attached to a satellite bus, and a solar array. “The objective of the S5 mission is to measure the feasibility and affordability of developing low cost constellations for routine and frequent updates to the GEO space catalog,” Blue Canyon Technologies said in its statement. The S5 satellite is attached to the Nusantara Satu satellite and will be until it reaches GEO, where it will separate, turn on, and start its mission. This is not dissimilar to Hispasat 30W-6 that also deployed a smallsat after launch last year.

blue canyon S5 smallsat
Blue Canyon Technologies announced in September 2017 it won an AFRL contract to provide the bus for an experimental smallsat called S5 for space surveillance applications. Credit: Blue Canyon Technologies

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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Mars InSight Has Been Busy

insight selfie
This is NASA InSight’s first full selfie on Mars. It displays the lander’s solar panels and deck. On top of the deck are its science instruments, weather sensor booms and UHF antenna. Credit: Nasa/JPL-Caltech.

So I have talked previously about the launch of the latest lander on Mars, named Mars Insight. Launched on the 5th of May 2018 by an Atlas V 401 from Vandenberg AFB, it began its 6 month journey to the red planet. Travelling across 484 million km it landed on 26th of November 2018. It landed much like the Curiosity and Phoenix missions with a parachute decent and then using rockets to lower the lander onto the surface gently. The mass of the lander is about 358 kg, but due to the gravity on Mars being two thirds less it only weighs 134.6 kg on the surface. Just a few hours after touchdown the Mars Odyssey orbiter relayed signals indicating that the solar panels had successfully opened, generating power. The relayed signal also contained a pair of images of the landing site. For the next few weeks InSight checked the health of the on board systems and monitor the weather and temperature of the landing site.

InSights workspace
This mosaic, made of 52 individual images from NASA’s InSight lander, shows the workspace where the spacecraft will eventually set its science instruments. The lavender annotation shows where InSight’s seismometer and heat flow probe can be placed. Credit: NASA/JPL-Caltech

The images relayed were used to find the best area to place the Seismometer instrument. There was then some time for scientists to evaluate the information and pick the best spot to place the sensitive instrument. On the 19th of December Insight used its 8ft robotic arm to pick up the Seismometer from the deck of the lander, and place it on the ground nearby. The position picked was one fairly free of rocks, making the leveling process easier. There was then another set of a few weeks to adjust the cable and ensure the SEIS instrument was perfectly placed. Then the arm picked up a protective cover from the lander to place over the instrument. This is designed to minimise noise from the surrounding atmosphere, being introduced from huge temperature changes and wind vibrations. This will allow the seismometer to pick up the tiny tremors that the planet may have. This is the first time another planet has been studied this way, the only other planetary body being the Moon. Viking 1 and 2 had seismometers on board but design flaws meant the results were inconclusive.

Temperature is one of the biggest issues with a mission like this. On Mars the temperature can range over 90 degrees Celsius in just a single sol (Martian day). The protective cover is ringed with a thermal barrier and a section of chain mail around the bottom. The wind and thermal shield has been specifically designed for the environment to moderate the temperatures. JPL has a history dealing with Mars temperatures from the many missions it has sent there including the Phoenix lander, and the Curiosity rover. The SEIS instrument was provided by the French Space Agency CNES, and developed by the Institut de Physique du Globe de Paris, with JPL building the wind and thermal shield. There is also a great British part of the instrument with some of the silicon sensors designed and fabricated by Imperial College London. The microseismometers were designed to pick up the faintest seismic activity from the surface. Scientists from Oxford’s Department of Physics also supported the development, and the Rutherford Appleton Laboratory’s RAL Space worked closely with the team to develop the front electronics of the instrument as well as the space qualification.

SEIS instrument cutaway
Cutaway illustration showing interior components of SEIS. Credit: NASA/JPL-Caltech/CNES/IPGP
One of the microseismometer sensors, carved from a single piece of silicon 25mm square. Credit: Imperial College/T.Pike.

On the 12th of February the lander deployed the HP3 package onto the surface. Known as the Heat Flow and Physical Properties Package, it was placed about a meter away from the seismometer. The Idea of HP3 is to measure the heat flow through Mars’s subsurface, hopefully helping scientists to figure out how much energy it takes to build a rocky planet like Mars. An interesting instrument, it has a self-hammering spike, or mole, allowing it to burrow up to 5m below the surface. This is much deeper than any previous mission. Viking 1 only scooped down 8.6 inches, and the predecessor of Insight, Phoenix dug to 7 inches. The probe was provided by the German Aerospace Centre (DLR). A tether attached to the top of the mole features heat sensors to measure the temperature of the Martian subsurface. Heat sensors in the mole itself will measure the soils thermal conductivity (how easily the heat moves through the surface). The mole plans to stop every 50 centimetres to take the measurements, as the hammering creates friction, releasing heat that would likely impact the instruments readings. It is then heated up by 28 degrees Celsius over 24 hours, with the temperature sensors measuring how rapidly this happens.

A GIF of the Insight lander placing the instruments on the ground. Credit: NASA/JPL-Caltech

Along with the Insight lander, the launch also contained a new first, a pair of cubesats known as MarCO-1 and MarCO-2. The size of small suitcases the pair were the first cubesats to enter and work in deep space. The team nicknamed the WALL-E and EVE, and they functioned as communications relays during the insight landing, beaming back data from the decent, along with the first image. WALL-E also managed to capture its own great images of Mars as it soared past it. The mission cost was about $18.5 million, much less than most missions, and was designed by JPL as a technology demonstrator mission. Neither is still in contact with Earth, with WALL-E losing contact on the 29th of December 18, and EVA losing contact on the 4th of January 19. JPL says they will attempt to contact the pair again in the future, but it is unlikely. The MarCO satellites will still live on though, with some of the spare parts going towards other cubesat missions, including experimental radios, antennas and propulsion systems. They also pushed the idea of using commercial parts to develop the system.

Engineer Joel Steinkraus uses sunlight to test the solar arrays on one of the Mars Cube One (MarCO) spacecraft at NASA’s Jet Propulsion Laboratory. Credit: NASA/JPL-Caltech
MarCO-B, one of the experimental Mars Cube One (MarCO) CubeSats, took these images as it approached Mars. Credit: NASA/JPL-Caltech

Just as an addition, there is a great comic that can be found here about Mars Insight, by the oatmeal. It is worth a quick read.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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Snowy Day at Harwell

So Oxfordshire got a big helping of snow in the last few years, and although Harwell campus wasn’t shut immediately it allowed for a great walk into work from the bus stop. It was a great opportunity for a few photos, and I decided to make this post to highlight some of my favourites.

snowy trees next to the cricket pitch
Snowy trees next to the cricket pitch.
snowy trees next to the road from Thomson entrance
A view towards the cricket pavillion from the edge of the pitch.
view from cricket pitch
A view across the road from the cricket pitches.
Thomson entrance
The Thomson entrance with a snowy cover.
Snowy fence
A view through the fence with a heavy helping of snow.
Campus HQ
Campus HQ from the Thomson entrance.
Snowy campus HQ
Campus HQ from the entrance, flag flying.
Quad One
A view towards the Quad One section of campus, and the new gym.
Campus pond
The pond frozen over, still wouldn’t skate on it though.
Oxford Space Systems
The Oxford Space Systems building and connected businesses with a snowy front lawn.
On top of the mound
Some undisturbed trees on top of the STFC mound.
Fermi Avenue
Fermi Avenue as the snow started up again.
Satellite Applications Catapult
Satellite Applications Catapult from the bus stop.
Bus stop
Bus stops with a few weary travellers hoping the busses are still running

Thank you for taking a look at my photos of a snow covered Harwell campus. Take a look at my other posts if you are interested in space, electronics, or general history, especially about the Harwell campus. If you are interested, follow me on Twitter to get updates on projects I am currently working on. Most of all, thank you for taking the time to read my posts.

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Eighth Set of Iridium NEXT satellites launched

flying falcon 9
A falcon 9 launching from Vandenberg AFB in the early hours of the morning. Credit: SpaceX

At 15:31 UTC on January the 11th 2019 an already flown Falcon 9 was the first SpaceX rocket flown in 2019. Launching from Vandenberg Air Force Base in California, it launched ten more Iridium NEXT satellites. The 70 metre high rocket with its 9 merlin 1D engines is the first of 18 expected flights this year for SpaceX. A surprisingly clear day for Vandenberg, the Falcon 9 flew over the Pacific Ocean early in the morning (local time) giving a great view of the launch. The Falcon 9 first stage booster successfully landed back on Earth for a second time, landing on the autonomous drone ship “Just Read the Instructions”.

vandenberg launch
A great view of the Falcon 9 launching with another 10 Iridium NEXT satellites aboard, finishing up the set. Credit: SpaceX
The mission patch of the Iridium NEXT 8 mission.

The booster used for this mission was B1049.2, which had previously flown on Telstar 18V mission, making this the second time this Block 5 first stage has flown. The 1.71 million pounds of thrust took the 9,600 kg payload towards a Polar Low Earth Orbit, like the other Iridium NEXT satellites. The rocket deployed the satellites one at a time over a roughly 15 minute period, around 30 minutes into the flight. Each of the 1,896-pound (860-kilogram) Iridium Next satellites will use their own thrusters to climb into a higher 476-mile-high (780-kilometer) to orbit, where six of the new spacecraft will rendezvous with the last of the old Block 1 satellites.

NEXT satellites
The Iridium Next satellites were connected to their dispensers inside a clean room at Vandenberg Air Force Base, California, before mating to the Falcon 9 rocket. Credit: Iridium
The SpaceX rocket high above the ground at Vandenberg, CA. 10 Iridium NEXT satellites aboard. Credit: SpaceX

This mission of ten more upgraded spacecraft has completed the build-out of Iridium’s modernised $3 billion global communications network. They are setting up for the planned debut of new broadband and aircraft tracking services in the coming months. This completes the 75 payloads on eight Falcon 9 missions since January 2017. The idea was to upgrade the old voice and data relay networks currently still in use. Iridium ordered 81 Iridium NEXT satellites from Thales Alenia Space and Northrop Grumman Innovation Systems, which were built in Gilbert, Arizona. Two weeks after the maiden flight of the Falcon 9 in 2010 Iridium announced a nearly $500 million contract for SpaceX to deliver the satellites to orbit. The initial plan was to start launching in 2015, finishing around 2017. Delays pushed by two Falcon 9 problems in 2015 and 2016 pushed the schedule back. In the end only 75 of the planned 81 have been launched, with 6 being flight spares. They could be launched to be additional backups for the system.

Falcon 9
A photo showing the raw power of the Merlin 1D engines launching the Falcon 9. Credit: SpaceX

The old satellites, that were built by Lockheed Martin had an initial lifespan of 7 years, and have way outlived their planned life. Engineers are currently deactivating the retiring satellites as the new stations arrive in orbit. Most of them have been maneuvered out of orbit to fall back to Earth and burn up in the atmosphere. They have usually gone through a process of “passivation” where the batteries and propellant tanks are drained to minimise chances of them exploding at some point in the future. Iridium satellites have also been a popular sight for astronomers, with “Iridium flares” becoming a commonly used term. It is where reflective parts of a satellite catch a glint from the sun and show up on the ground as a flash, sometimes 5-20 seconds long. They can be as bright as magnitude -8, which is brighter than Venus in the sky. Iridium satellites have been known to be a noticeable cause of these flares, leading to the name “Iridium flares”. The new satellites have a different antenna shape meaning they do not reflect in the same way.

Iridium flares
An iridium flare over Butser Hill, Hampshire. Credit: Nikki Young (@astro_niks)

As well as majorly upgraded telecommunications ability the satellites also host a radio receiver for Aireon, an affiliate of Iridium. Aireon work with traffic control authorities in Europe and Canada. The new instrumentation will track air traffic worldwide, including planes travelling outside the range of conventional ground based radar. This completion of the network has allowed the services provided by Aireon to take a big step forward towards starting operations. When airplanes fly out of radar range, pilots are typically instructed to maintain a certain course and altitude, ensuring 30-to-100 miles (about 50-150 km) of separation between aircraft for safety purposes. With real-time global monitoring, those requirements could be relaxed. According to Aireon the certification of the system should be complete by March, allowing operational trials over the North Atlantic.

merlin engines
A photo showing the Raw power of the nine Merlin 1D engines, exposed to see the flames in a better light. Credit: SpaceX

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on.

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The Genius of Bob Widlar

National Semiconductor Ad
A famous National Semiconductor ad based on the Widlar Salute and methedology

If you are at all interested in early IC design, especially that in the start of silicon valley, it’s likely that you will have come across the name Bob Widlar. If you have not heard of him then this post may shed some light on an early pioneer of the semiconductor industry. Not just a great hardware engineer, arguably a legendary one. Shaping integrated circuit designs for over a decade he created circuits still in use today, and some of the most famous chips ever. Including the uA702, the first linear IC operational amplifier and the LM109, the first high power voltage regulator. Although a great engineer he was famous for his pranks, and odd office habits. He definitely would not like the current state of corporations, with a bohemian look on life Bob Widlar can definitely be described as eccentric.

Bob widlar salute
Bob Widlar showing the official Widlar salute.

In the late 1960’s and 70’s the semiconductor industry was like something out of a scene in a wild west film. The bars around Silicon Valley were packed day and night with engineers creating innovative circuits and designs left and right, and Bob was right there in the middle of it all. I think a key point to note is that he was partial to his alcohol, for better or worse there are accounts that he wouldn’t make a speech until the had his allotment of scotch or wine. This wasn’t uncommon for the time though, everyone around him was likely the same. The History of Semiconductor Engineering (a very expensive book) describes, “Bob was a fiercely independent individual, very happy to be by himself, and he did everything in a stunning way, which was absolutely natural to him, but completely weird to so-called ‘normal people’.” Basically he didn’t care what other people thought about him. If you want to change an entire industry you have to upset a few people on your way, so this mindset might be best.

Bob Widlar disliked digital circuitry
It could be said that Bob widlar was not a fan of digital circuitry.

There isn’t much known about his early life, and reportedly rarely spoke about it. We do know thought that electronics played a huge role in his early life as his dad was a self taught radio engineer. His father worked at a local radio station so Bob had access to ultra-high frequency transmitters. At 15 he was featured in his local newspaper as an electronics designer who could fix radio and TV sets. Allegedly he also played pranks on the local police using radios, but there is no known details. The passion for electronics continued on when he joined the United States Air Force in 1958. He was responsible for teaching fellow recruits in the use of electronic equipment such as radios. During this time he actually wrote a book, his first, Introduction to Semiconductor Devices. This seems to be a slightly different person to the famous side of Bob Widlar. Some say that his “liberal mind” wasn’t a good fit for the military environment, but his early performance reviews suggest otherwise. His superiors noted his superior electronics and communications skills, they also noted that he had an above average ability to use clear concise words to express himself, and always strived for perfection. In areas of improvement he was recommended to stop dramatising his frustrations at inefficiencies that exist”. This might be closer to the famous widlar. He then left the service in 1961 for unknown reasons, and joined the Ball Brother Research Corporation in Boulder, Colorado. There he helped develop analog and digital equipment for NASA. He was simultaneously studying for a degree with the University of Colorado and graduated in the summer of 1963.

His work at Ball Brothers brought him in contact with Jean Heorni and Sheldon Roberts (who invented radiation hardened transistors), some of the founders of Fairchild Semiconductor. They breached professional ethics by hiring him, a key employee of their customer. He apparently arrived at the interview intoxicated and told the R&D manager what he thought of Fairchild’s analog circuits, saying”what they are doing is bullshit”. He had a second interview and was hired even with the objections by the initial interviewers. His first task at Fairchild was to target IC reliability by improving the fabrication process. He managed to reduce the price of the planar process, and showed he could improve his own bosses designs and squeezed him out of the company. At this point Fairchild only had a lineup of three analog IC’s, all designed for the military, all amplifiers. They were all built inefficiently, like a conventional circuit with discrete devices, creating a sort of hybrid IC. The famous Gordon Moore (of Moore’s Law fame) wanted the company to favour digital IC’s as they were cheaper, easier to design and allowed high volume. Widlar opposed the strategy and held digital electronics in low esteem, famously saying “every idiot can count to one”. Along with the process engineer David Talbert, they rushed through Widlars designs for new and improved analog IC’s, changing the industry as they did so. He managed to remove the need for big resistors and capacitors in IC’s, and truly grasped the planar process. This is when he created the μA702, the first true linear integrated circuit, and the first monolithic operational amplifier.

Bob and a group of engineers at National Semiconductor.

He also created the μA709, another legendary chip. This moved Fairchild to become the leader in the field of linear IC’s. Their circuits were sold out for two years. Some say that at one point Widlar designed and Talbert made 80% of the linear circuits in the world. The problem was that Fairchild never shared the massive profits with them. So he took up a job with National Semiconductor in 1965, taking a huge amount of stock as part of the deal. He refused to do the exit interview at Fairchild and wrote one line to them “I want to be RICH!”. Oddly, Fairchild continued to pay his salary until 1966, Widlar said “Maybe they did not believe that I was actually leaving. Some people are really a little slow.” By 1966 they had set up the epitaxial process at Santa Clara, and created the industry’s first linear regulator. The LM100, a revolutionary new circuit became a flagship product, soon followed up in 1967 with the LM101, an op amp with highly improved performance due to a simple yet robust design. He followed it up with many more improvements to amplifiers, with higher bandwidth, voltage and gain. As well as the famous Widlar current source, he also managed to harness the bandgap phenomenon and built the bandgap voltage reference. This allowed the design of the LM109, a voltage regulator with a power transistor and precise voltage source on one die, something never seen before. By this time Fairchild had gone into a massive decline while National Semiconductor had rocketed up the food chain. In December 1970 he resigned from National Semiconductor and cashed in his stock for $1 million, apparently due to payment issues. He retired to Puerto Rico at the age of 33. The next four years he spent as a consultant.

Widlar current source. Original drawing from the 1967 U.S. patent.

He did come back to National Semiconductor in 1974 as a consultant. During the short stints he spent there he developed the LM12 power amplifier and and the LM10 ultra-low voltage amplifier. These have stayed in production until the 21st century, with the LM10 not even having a reasonable clone for the next decade. in 1981 he spent three years starting Linear Technologies, but this relationship eventually fell apart three years later over patent rights, and his shares were forcibly bought. For the remainder of his life he worked at National semiconductor until 1991 when he died of a heart attack at the age of 53. He had apparently taken up running late in his life and was much healthier. One of his fellow engineers Bob Pease said the damage was done in the first 20 years.

Bob Widlar standing over artwork of the LM10 power amplifier

On top of his famously eccentric nature, fighting in bars and unceremoniously leaving companies he was a well known prankster. The most famous one was the day he brought a sheep to work. The reason was to save money for the company by using it as a lawn mower. He brought it in the back of his Mercedes-Benz convertible for the day. The management not particularly pleased refused to comment. Widlar even invited some young photojournalists to document the event. After the day he left the sheep in a local bar and it was “mysteriously stolen”. On another note he apparently disliked people coming into his office and being excessively loud. He therefore built what is now known as a Hassler circuit which emits a high pitched sound whenever it hears something too loud. In the same vein he also blew up a public address speaker he found annoying with firecrackers! As an analog engineer and highly skilled with high frequency transmitters he once traced one of his problems to interference from the control tower of San Jose airport. In the Widlar way he called up the airport and demanded that they shut down the transmitter. He did have a thing about faulty components and problems, as any electronic engineer can appreciate. If he had spent a day trying to fix a fault just to find a simple component was the cause he would take it out to the workshop an pulverize it with a hammer. The practice now known as Widlarizing usually uses a sledgehammer and requires the component to be smashed so small you don’t even need to sweep it up off the floor. This was so the component couldn’t cause anyone else more problems.

Bob Widlar with the famous sheep, trying to get it to mow the lawn for him. The Mercedes is in the background, badly parked.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or general history. If you are interested, follow me on Twitter to get updates on projects I am currently working on. Most of all, thank you for taking the time to read my posts.

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How Satellite Data Can Aid Archeology

For hundreds of years, maybe even thousands, humans have been digging holes, trying to unearth treasures of a bygone age. It is a messy affair, lots of shoveling and moving large amounts of dirt or sand. When it gets down to it small trowels may need to be used or even little brushes. How do we know where to dig? Well sometimes there are already existing structures, or the remnants of buildings. There could also be a building that has been there a long time. We just have to find hints that something interesting is under the ground. Archaeology can find things like pottery, tools and coins, but also parts of old structures. The problem is that more often than not these things are buried, else we would already know about them. In recent years archaeologists have used remote sensing methods to have a basic look underneath the ground before they dig it up. Basically the devices send a signal into the ground and see what gets reflected back. This can be very time consuming, moving equipment to a random field and spend all day setting up and getting reasonable measurements. Now with the increase of satellite technology there is a new way to look for new sites.

Inverted kite aerial photo of an excavation of a Roman site at Nesley near Tetbury in Gloucestershire. Taken on a kite line. Credit: Dr John Wells

The method of using satellite imagery, such as that found on Google Maps, is generally referred to as an aerial survey. Traditionally this was done using cameras attached to an airplane, balloon or UAV’s. People have also been known to use kites! These pictures can be useful to help map a large area, or a site that is particularly complex. Plus if they are taken fairly often then they can be used to document to progress and status of the dig. This angle of image can also help to detect things not obvious from the ground. Things like different coloured soil/sand, or locations of certain types/colours of flowers can hint at a buried structure or wall. When solid rocks develop under plants they tend to grow slower, so a wall may actually be fairly obvious if looked at over time. Certain plants such as ripening grain changes colour rapidly, and if anything slows it down then it is noticeable compared to the other grain. When looking at different times of day the shadows could show areas of a field that are slightly raised from its surrounding.

In this satellite image, the white arrows show a potential previously unknown buried pyramid and the black arrows other structures which have yet to be investigated. Credit: National Research Council, Italy.

With more and more Earth monitoring satellites going up all the time, companies like Planet Labs can now offer a satellite image of a specified part of land with updated images in the days and sometimes hours timescale. There have also been changes in the type of satellite going up, they are no longer just taking standard images. Modern technology allows the use of sensors seeing different wavelengths of light. The different bands of the electromagnetic spectrum can tell us different things about the thing you are looking at, and most of the spectrum, the human eye cannot see. Most of these satellites are designed to be used to look at weather conditions, specifically things like clouds and effect on the ground. Many modern weather satellites use microwave sensors to probe the ground. Much like microwave radar used to track airplanes, the satellites can send a signal towards the ground, and the signal that gets reflected back can say plenty about the surface. This is similar to the way ground penetrating radar works. SAR (Synthetic Aperture Radar) satellites are an example of this technology. There is also a good portion of satellites with Infrared spectrum sensors. This band is often giving data on aspects like temperature, showing how different sections of land are reacting to weather conditions can say plenty about what the ground is made of. There are also other methods to map the surface, such as LIDAR which is used in range finding applications, showing distances from the satellite to the ground.

Airborne laser-scanning technology, called LiDAR, provides a 3-D map of part of the Maya city at Caracol in Belize. LiDAR cuts through the jungle to reveal the hidden features beneath, a revolution in the study of ancient Maya landscapes. Credit: Courtesy Arlen Chase

Even though this is a fairly new technology for archaeology, there have been some significant uses of it. One of the most prominent uses have been to study the Maya civilization in ancient Mesoamerica. A particular area of interest is the Petén region of northern Guatemala. Very dense forest, and little to no modern settlements in the area make it difficult to study. Remote sensing has allowed scientists to study potential causeways and canals used by this early civilization. There have also been hints at cisterns and temples and buildings that they may have lived in. This allows for archaeologists to have a much better idea of where to look, without ever having to visit the jungle. In Peru, a group of Italian scientists have been getting results using satellite imagery. They have managed to get images of a buried settlement, including a pyramid in a riverbed. The North of Peru has also been known to be a haven for clandestine excavations. Satellite data has been useful to map and monitor archaeological looting. There have also been attempts to find lost cities such as Iram of the Lost Pillars in the Arabian Peninsula. The researchers found interesting information on old trade routes and uncovered a previously unknown settlement. There is also an award winning TED talk by Dr Sarah Parcak on using citizen science to search for sub-surface remains, Using normal people looking at satellite images they have prospectively found several significant sites in various parts of Egypt and the ancient Roman Empire.

A LiDAR image of the Caana complex at the heart of Caracol, at left, shows the tree canopy surrounding a 140-foot-tall building (in an aerial photo at right). The lasers also penetrate the jungle to reveal structures hidden by that overgrowth. Credit: Courtesy Arlen Chase.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or general history. If you are interested, follow me on Twitter to get updates on projects I am currently working on. Most of all, thank you for taking the time to read my posts.

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A Great Start to the Space Year

2018 was a great year for space, but it was barely a few days into 2019 and three amazing achievements in space have happened. We had new Horizons studying the furthest object studied in space, the Chinese space agency landing a rover on the far side of the Moon, and OSIRIS-REx mission reached bennu.

New Horizons

By far the biggest news in the space sector recently, New Horizons officially flew by object 2014 MU69, the outermost close encounter of any Solar System object. Launching in 2016, New Horizons was a mission designed to help us understand the worlds at the edge of our Solar System. The biggest part of the mission was in 2015 when it made the first reconnaissance of the dwarf planet Pluto, producing some amazing photos. After that it kept venturing out into the Kuiper Belt to study more mysterious objects. The spacecraft is helping us to understand the basic questions about the surface properties, interior makeup, geology and atmosphere of the bodies it passes. The exploration of the Kuiper belt is one of the big priorities in planetary science currently. New Horizons fits into this plan, by seeing how Pluto and its Moons “fit in” to the other objects in the Solar System. It has already aided in finding four previously unknown Moons of Pluto, and studied the known Moon Charon in much more detail.

New Horizons Artist
An artistic impression of what New Horizons looked like when it passed Pluto and Charon. Credit: NASA Goddard Media Studios.

New Horizons was designed, built and is operated by The John Hopkins University Applied Physics Laboratory in Laurel, Maryland. Alan Stern of the Southwest Research Institute (SwRI) in Boulder, Colorado is the principal investigator. It flew by the Kuiper belt object 2014 MU69 barely a few hours into the new year at 05:33 UTC on January 1st 2019. The flyby technically ends on January 9th, where it switches from 3-axis mode to spin mode. This is the beginning of the downlink phase which could run for around 18 months! This is because it is so far away, the frequency (and therefore the data rate) is much lower than if the spacecraft was close. The current extended mission is planned to last until April 30th, 2021. If still operational there may be a new extended mission, but it has very limited fuel at about 11kg. The craft could in theory visit another Kuiper Belt object. If it lasts until the mid 2030’s it will join Voyager 2 in the Heliosphere, but based on the RTG it may run out about then.

Ultima Thule
Image of 2014 MU69, taken 30 minutes before closest approach from a distance of 28,000 km (17,000 mi). Credit: NASA/John Hopkins Applied Physics Laboratory.


On January 3rd 2019 at 02:26 UTC China’s Chang’e-4 spacecraft successfully landed on the far side of the Moon. The first ever soft landing on the far side of the Moon, up until this point we only has remotely sensed images. The target of the spacecraft was the Von Kármán crater, located within the South Pole-Aitken basin. This is where an ancient lunar impact may have exposed some of the Moon’s mantle. The plan is to study this region directly with the rover and the lander. It also allows for a close up look at the far side of the Moon, which could be a perfect place for science applications such as radio astronomy. As there is no direct line of sight to the far side of the Moon they need a relay satellite. The satellite that China launched is the Queqiao relay satellite, launched in May 2018.

An image of the rover similar to the Chang’e-3’s rover. Credit: CNSA.


Coming into the new year, on December 31st OSIRIS-REx entered orbit around Bennu. The orbit is at around 1.75 km (just over a mile), and is the place it will be doing an extensive remote sensing campaign. 101955 Bennu, or 1999 RQ36, is a carbonaceous asteroid in the Apollo group. Discovered in 1999, it has a 1 in 2700 chance of impacting Earth between 2175 and 2199. The name Bennu references the Egyptian mythological bird associated with the sun, creation and rebirth. The OSIRIS-REx mission is a sample return mission to the asteroid Bennu. Its goal is to obtain a sample of at least 60g and then bring that sample back to Earth for scientific study. The aim is to help scientists to learn about the formation and evolution of Solar System in its initial stages of planet formation and the source of organic compounds that eventually lead to life. If the mission is successful on September 24th 2023 it will be the first US spacecraft to return samples from an asteroid.

Asteroid Bennu, imaged by the OSIRIS-REx probe (3 December 2018). Credit: NASA/ Goddard/ University of Arizona.

Thank you for reading, take a look at my other posts if you are interested in space, electronics, or military history. If you are interested, follow me on Twitter to get updates on projects I am currently working on. Most of all, thank you for taking the time to read my posts this year! So all have a Happy New Year, and here’s to a great 2019 in space!

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