Meet the “Scene Select Mechanism”—Part of the LDCM Thermal Infrared Sensor
Meet the “Scene Select Mechanism”—Part of the LDCM Thermal Infrared Sensor
Engineer (in a “bunny suit”) working on the Scene Select Mechanism of the Thermal Infrared Sensor (TIRS) that will fly on LDCM.
NASA
Special Topics: LDCM and LDCM Components
The Scene Select Mechanism is an apparatus that rotates the LDCM Thermal Infrared Sensor (TIRS) mirror among three scenes: the Earth view (“nadir;” when imaging the Earth), and two calibration views (one of a warm blackbody carried onboard and the other of a deep-space cold view).
The Earth view requirements for instrument pointing are very stringent, correct image positioning depends on precise pointing and that position must be returned to faithfully after each calibration sequence. The requirement for the Thermal Infrared Sensor (TIRS) is to image up to 44 minutes continuously, which corresponds to the longest uninterrupted landmass pass that TIRS needs to image before traveling over water—when the calibration sequence can be performed again. (This long-land path curves from Northern Russia to the southern tip of Africa.)
Bunny suit: The TIRS instrument is kept in a cleanroom and anyone working on it must wear cleanroom clothing that minimizes particulates coming from a person’s clothing. Prior to entering the cleanroom, each person also takes an “air shower” which blows any excess dust off of them before entering the cleanroom. Inside the Class 10,000 cleanroom are filters which continuously filter the air inside to ensure there are no more than 10,000 particles greater than 0.5 microns in size within a cubic foot of air (the average home has about 300,000 particles per cubic foot).
Mirrors for the LDCM Operational Land Imager (OLI) Telescope.
NASA
Special Topics: LDCM and LDCM Components
The OLI telescope uses a four-mirror compact design. The optics are positioned inside a lightweight, yet highly stable, carbon composite optical bench (i.e., a substrate on which the optics are mounted) that has special features to control undesired stray light (stray light is any light entering the optics from someplace other than the observed Earth surface, or imaging “target”).
Because OLI is a push-broom instrument, as opposed to a scanner (or “whisk-broom”), it has a wide field-of-view to cover the entire ground swath width. Wide field-of-view telescopes are generally susceptible to stray light, so the OLI telescope is designed for improved stray light control. The number and shapes of the mirrors meet the required optical design parameters, like focal length, for example, within a size that also meets the volume and mass requirements for the instrument.
Note: The previous Landsat sensors have used scanner or “whisk-broom” technology. This means that a mirror scans from side-to-side across the satellite path directing light into the instrument detectors. The OLI uses push-broom technology meaning that an array of detectors is used to image the entire swath/width of the satellite path simultaneously.
Landsat Data Continuity Mission Becomes an Observatory
Landsat Data Continuity Mission Becomes an Observatory
TIRS being hoisted into place on the LDCM satellite in Gilbert, Ariz.
Orbital Science Corp
• Engineers at Orbital Sciences Corporation, Gilbert, Ariz., have installed the Thermal Infrared Sensor (TIRS) instrument back onto to the Landsat Data Continuity Mission (LDCM) spacecraft. With both the Operational Land Imager (OLI) and TIRS instruments now on the spacecraft, LDCM is a complete observatory.After the TIRS instrument was shipped to Orbital in February, engineers discovered that helium had leaked from the TIRS cryogenic cooler. The cooler keeps the detectors extremely cold, which is required for the instrument to detect thermal infrared radiation emitted from Earth. The leak was quickly repaired, the cooler was re-pressurized with helium, and TIRS was re-installed onto the instrument deck of the spacecraft. Once the TIRS instrument is electrically connected later this month, TIRS will be ready to begin environmental testing with the rest of the observatory.
The engineering team at NASA’s Goddard Space Flight Center in Greenbelt, Md., built TIRS on an accelerated schedule, going from a design on paper to a completed instrument in 43 months. An instrument of this type usually takes another year to complete.
Under contract to NASA, Orbital is responsible for providing the spacecraft bus, installing the science instruments and performing system-level integration and testing of the Observatory prior to launch. Ball Aerospace & Technologies Corp. built the OLI. The USGS developed the LDCM ground system.
An artist’s impression of gravitational waves generated by binary neutron stars.
Credits: R. Hurt/Caltech-JPL
by Kat Troche of the Astronomical Society of the Pacific
September 2025 marks ten years since the first direct detection of gravitational waves as predicted by Albert Einstein’s 1916 theory of General Relativity. These invisible ripples in space were first directly detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). Traveling at the speed of light (~186,000 miles per second), these waves stretch and squeeze the fabric of space itself, changing the distance between objects as they pass.
Waves In Space
Gravitational waves are created when massive objects accelerate in space, especially in violent events. LIGO detected the first gravitational waves when two black holes, orbiting one another, finally merged, creating ripples in space-time. But these waves are not exclusive to black holes. If a star were to go supernova, it could produce the same effect. Neutron stars can also create these waves for various reasons. While these waves are invisible to the human eye, this animation from NASA’s Science Visualization Studio shows the merger of two black holes and the waves they create in the process.
Two black holes orbit each other, generating space-time ripples called gravitational waves in this animation. As the black holes get closer, the waves increase in until they merge completely.
NASA’s Goddard Space Flight Center Conceptual Image Lab
How It Works
A gravitational wave observatory, like LIGO, is built with two tunnels, each approximately 2.5 miles long, arranged in an “L” shape. At the end of each tunnel, a highly polished 40 kg mirror (about 16 inches across) is mounted; this will reflect the laser beam that is sent from the observatory. A laser beam is sent from the observatory room and split into two, with equal parts traveling down each tunnel, bouncing off the mirrors at the end. When the beams return, they are recombined. If the arm lengths are perfectly equal, the light waves cancel out in just the right way, producing darkness at the detector. But if a gravitational wave passes, it slightly stretches one arm while squeezing the other, so the returning beams no longer cancel perfectly, creating a flicker of light that reveals the wave’s presence.
When a gravitational wave passes by Earth, it squeezes and stretches space. LIGO can detect this squeezing and stretching. Each LIGO observatory has two “arms” that are each more than 2 miles (4 kilometers) long. A passing gravitational wave causes the length of the arms to change slightly. The observatory uses lasers, mirrors, and extremely sensitive instruments to detect these tiny changes.
NASA
The actual detection happens at the point of recombination, when even a minuscule stretching of one arm and squeezing of the other changes how long it takes the laser beams to return. This difference produces a measurable shift in the interference pattern. To be certain that the signal is real and not local noise, both LIGO observatories — one in Washington State (LIGO Hanford) and the other in Louisiana (LIGO Livingston) — must record the same pattern within milliseconds. When they do, it’s confirmation of a gravitational wave rippling through Earth. We don’t feel these waves as they pass through our planet, but we now have a method of detecting them!
While the average person may not have a laser interferometer lying around in the backyard, you can help with two projects geared toward detecting gravitational waves and the black holes that contribute to them:
Black Hole Hunters:Using data from the TESS satellite, you would study graphs of how the brightness of stars changes over time, looking for an effect called gravitational microlensing. This lensing effect can indicate that a massive object has passed in front of a star, such as a black hole.
Gravity Spy:You can help LIGO scientists with their gravitational wave research by looking for glitches that may mimic gravitational waves. By sorting out the mimics, we can train algorithms on how to detect the real thing.
You can also use gelatin, magnetic marbles, and a small mirror for a more hands-on demonstration on how gravitational waves move through space-time with JPL’s Dropping In With Gravitational Waves activity!
NASA, Blue Origin Invite Media to Attend Mars Mission Launch
A stylized illustration shows the twin ESCAPADE spacecraft entering Mars’ orbit.
Credits: James Rattray/Rocket Lab USA
NASA and Blue Origin are reopening media accreditation for the launch of the agency’s ESCAPADE (Escape and Plasma Acceleration and Dynamics Explorers) mission. The twin ESCAPADE spacecraft will study the solar wind’s interaction with Mars, providing insight into the planet’s real-time response to space weather and how solar activity drives atmospheric escape. This will be the second launch of Blue Origin’s New Glenn rocket.
Media interested in covering ESCAPADE launch activities must apply for media credentials. Media who previously applied for media credentials for the ESCAPADE launch do not need to reapply.
U.S. media and U.S. citizens representing international media must apply by 11:59 p.m. EDT on Monday, Oct. 13. Media accreditation requests should be submitted online to: https://media.ksc.nasa.gov.
Blue Origin is targeting later this fall for the launch of New Glenn’s second mission (NG-2) from Space Launch Complex 36 at Cape Canaveral Space Force Station in Florida. Accredited media will have the opportunity to participate in prelaunch media activities and cover the launch. Once a specific launch date is targeted, NASA and Blue Origin will communicate additional details regarding the media event schedule.
NASA will post updates on launch preparations for the twin Martian orbiters on the ESCAPADE blog.
The ESCAPADE mission is part of the NASA Small Innovative Missions for Planetary Exploration program and is funded by the agency’s Heliophysics Division. The mission is led by the University of California, Berkeley Space Sciences Laboratory, and Rocket Lab designed the spacecraft. The agency’s Launch Services Program, based at NASA’s Kennedy Space Center in Florida, secured launch services under the VADR (Venture-class Acquisition of Dedicated and Rideshare) contract.
