TESS is, as all should know, the transiting-exoplanet-survey-satellite. Yeah, i knoiw, it’s hard to keep track of them all.
https://www.nasa.gov/tess-transiting-exoplanet-survey-satellite

TESS satellite has started collecting science data. Over the next two years, it will look at almost the entire sky, searching for evidence of new planets:

Even before it started science operations, it spotted a comet.

Dang it. Can’t copy the address of a nice video here. Try looking at the top post of https://twitter.com/NASA_TESS

I don’t understand TESS. But then I didn’t understand Hubble.

Answer me this, how does it flip its axis every orbit to switch from one hemisphere to the other? It must use up an awful lot of fuel.

mollwollfumble said:

I don’t understand TESS. But then I didn’t understand Hubble.

Answer me this, how does it flip its axis every orbit to switch from one hemisphere to the other? It must use up an awful lot of fuel.

I suppose it must defy the laws of physics.

The Rev Dodgson said:

mollwollfumble said:

I don’t understand TESS. But then I didn’t understand Hubble.

Answer me this, how does it flip its axis every orbit to switch from one hemisphere to the other? It must use up an awful lot of fuel.

I suppose it must defy the laws of physics.

reaction wheels?

JudgeMental said:

The Rev Dodgson said:

mollwollfumble said:

I don’t understand TESS. But then I didn’t understand Hubble.

Answer me this, how does it flip its axis every orbit to switch from one hemisphere to the other? It must use up an awful lot of fuel.

I suppose it must defy the laws of physics.

reaction wheels?

“Over the two-year mission, TESS will employ a “stare and step” observation strategy. The four cameras will observe a 24-by-96-degree observation sector for 27 days, then the spacecraft will be reoriented to observe the next sector. The cameras will tile the sky with 13 observation sectors in each hemisphere, or a total of 26 observation sectors over the two-year mission.”

https://www.nasa.gov/sites/default/files/atoms/files/tesssciencewritersguidedraft23.pdf

JudgeMental said:

The Rev Dodgson said:

mollwollfumble said:

I don’t understand TESS. But then I didn’t understand Hubble.

Answer me this, how does it flip its axis every orbit to switch from one hemisphere to the other? It must use up an awful lot of fuel.

I suppose it must defy the laws of physics.

reaction wheels?

That would be what I’d like to choose. They would have to be very heavy I think, to turn the whole spacecraft 180 degrees.

Some TESS Optics. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150018419.pdf
The main differences between this and a conventional wide angle camera f/1.4 are:

• Some wide angle cameras allow 50% vignetting at the corners. TESS has no vignetting.
• Cooled to -75°C
• Compact with wide lenses
• Designed to minimise internal reflections
• Using CCD detectors with only 4 megapixels.

The lens hood is remarkably similar to the design I had for my “blind spot camera”.

esselte said:

“Over the two-year mission, TESS will employ a “stare and step” observation strategy. The four cameras will observe a 24-by-96-degree observation sector for 27 days, then the spacecraft will be reoriented to observe the next sector. The cameras will tile the sky with 13 observation sectors in each hemisphere, or a total of 26 observation sectors over the two-year mission.”

https://www.nasa.gov/sites/default/files/atoms/files/tesssciencewritersguidedraft23.pdf

Ah, then I totally misunderstood. TESS stares in the same direction for entire orbits, 27 days, and only switches hemispheres after a year. That’s a very low fuel usage option.

But that means that for most of the sky it can only see exoplanets that have three transits within 27 days! That’s so close that it orbits in about 9 days or less. They’re not going to get anything remotely Earthlike out of that. Except in polar regions.

OK, scratch TESS. It was a bad idea from the word go. But at least with a bit of luck it will have less light leakage (from one star to another) than Kepler.

mollwollfumble said:

“Over the two-year mission, TESS will employ a “stare and step” observation strategy. The four cameras will observe a 24-by-96-degree observation sector for 27 days, then the spacecraft will be reoriented to observe the next sector. The cameras will tile the sky with 13 observation sectors in each hemisphere, or a total of 26 observation sectors over the two-year mission.”

https://www.nasa.gov/sites/default/files/atoms/files/tesssciencewritersguidedraft23.pdf

Ah, then I totally misunderstood. TESS stares in the same direction for entire orbits, 27 days, and only switches hemispheres after a year. That’s a very low fuel usage option.

But that means that for most of the sky it can only see exoplanets that have three transits within 27 days! That’s so close that it orbits in about 9 days or less. They’re not going to get anything remotely Earthlike out of that. Except in polar regions.

OK, scratch TESS. It was a bad idea from the word go. But at least with a bit of luck it will have less light leakage (from one star to another) than Kepler.

13 observation sectors in each hemisphere @ 24 degrees “wide” per sector, 13*24=312 degrees coverage in each hemisphere; hemisphere is only 180 degrees, 312/180=1.733

So it looks like a lot of overlap on the sectors, 73% increasing the time spent observing each individual star is greater than 27 days.

Note I’m not a mathamologist or a astronician or anything like that. The above is more of a question than a statement. Please correct me on the stuff I have wrong.

esselte said:

mollwollfumble said:

“Over the two-year mission, TESS will employ a “stare and step” observation strategy. The four cameras will observe a 24-by-96-degree observation sector for 27 days, then the spacecraft will be reoriented to observe the next sector. The cameras will tile the sky with 13 observation sectors in each hemisphere, or a total of 26 observation sectors over the two-year mission.”

https://www.nasa.gov/sites/default/files/atoms/files/tesssciencewritersguidedraft23.pdf

Ah, then I totally misunderstood. TESS stares in the same direction for entire orbits, 27 days, and only switches hemispheres after a year. That’s a very low fuel usage option.

But that means that for most of the sky it can only see exoplanets that have three transits within 27 days! That’s so close that it orbits in about 9 days or less. They’re not going to get anything remotely Earthlike out of that. Except in polar regions.

OK, scratch TESS. It was a bad idea from the word go. But at least with a bit of luck it will have less light leakage (from one star to another) than Kepler.

13 observation sectors in each hemisphere @ 24 degrees “wide” per sector, 13*24=312 degrees coverage in each hemisphere; hemisphere is only 180 degrees, 312/180=1.733

So it looks like a lot of overlap on the sectors, 73% increasing the time spent observing each individual star is greater than 27 days.

Note I’m not a mathamologist or a astronician or anything like that. The above is more of a question than a statement. Please correct me on the stuff I have wrong.

Tryig again with correct quote stuff.

TESS was explained pretty well on The Search for a Second Earth on ABC the other night (last 10 mins).

It uses coronagraphs to mask out the star’s light (this looks all very analogue and a bit dodgy to me but apparently it works) and produce spectragrams of the planet’s atmosphere.

esselte said:

13 observation sectors in each hemisphere @ 24 degrees “wide” per sector, 13*24=312 degrees coverage in each hemisphere; hemisphere is only 180 degrees, 312/180=1.733

So it looks like a lot of overlap on the sectors, 73% increasing the time spent observing each individual star is greater than 27 days.

Note I’m not a mathamologist or a astronician or anything like that. The above is more of a question than a statement. Please correct me on the stuff I have wrong.

I’ll accept your maths as correct.

Yes, the overlap is substantial, but only at the poles. There’s no overlap at all within 30 degrees of the Earth’s equator, in fact there are gaps. A complete two-fold overlap (still just 54 days, planet year shorter than 18 days) occurs at 70 degrees from the equator. A complete four fold overlap (still 36 day orbit, way closer in that Mercury’s 88 days) occurs at 75 degrees from the Earth’s equator. At some higher latitudes the seeing is almost continuous for 1 year. But even one year of continuous seeing isn’t long to pick up any orbits as far out as twice as close as Venus.

A correction. By equator I mean ecliptic equator, ignoring the tilt of the Earth’s axis.

TESS Sector 1 Pointing
Start date: Jul 25 2018
End date: Aug 23 – 24 2018

Then sector 2, sector 3 etc.

Data release products will include: Raw full frame images, calibrated full frame images, target pixels, light curves, flat fields, pixel response function, and lists of TESS Objects of Interest (TOIs). … stacks the 2-second images in groups of 60 to produce the 2-minute or 30-minute cadence for observations. Postage stamps (at 2-minute cadence, nominally 10×10 pixels in size) and FFIs (at 30-minute cadence). Sending results to Earth every 13.7 days. What use is a “postage stamp” size? Does the stacking eliminate cosmic rays?

It’s the light curves and objects of interest that most interest me. But for … I wonder. What frequency is it viewing at? Can we get pretty pictures out of this like the ones from WISE?

TESS’s two-year all-sky survey will focus on nearby G, K, and M type stars with apparent magnitudes brighter than magnitude 12. … a bandpass range of 600 to 1000 nm. That’s good. Near IR starts at 700 nm. By viewing in red and infrared it eliminates the great brightness range generated by hot blue and white stars. That also helps a lot in distinguishing between binary stars and planets.

Or does it? A faint red dwarf or hot brown dwarf can masquerade as a planet in an eclipse. The drop in star brightness is countered by the brightness of the companion, so a binary star where the two stars have similar masses has the same light drop as a small planet. A binary star like this will take longer to pass the limb of the disk, except where the planet is far from the equator, whereupon the two will again look similar. With Kepler, I found that the assumption of planet rather than star resulted in a statistically impossible situation where nearly every one of the planets crossed a long way from the equator. Binary stars were masquerading as planets, but it was impossible to determine which individual planets were in fact binary stars. I also found that there were a lot more binary stars than planets.

Video on TESS and its launch from SpaceX
https://www.youtube.com/watch?v=aY-0uBIYYKk

Great images of rocket nozzle glowing red in space. Includes onboard images of landing on tail, and snow in space.

Also:
https://www.youtube.com/watch?v=-2SECBi-AP8

and ESA Cheops, JWST, WFIRST, ESA PLATO, ARIEL:
https://www.youtube.com/watch?v=w8tx4bXm3Ko

mollwollfumble said:

Video on TESS and its launch from SpaceX
https://www.youtube.com/watch?v=aY-0uBIYYKk

Great images of rocket nozzle glowing red in space. Includes onboard images of landing on tail, and snow in space.

Also:
https://www.youtube.com/watch?v=-2SECBi-AP8

and ESA Cheops, JWST, WFIRST, ESA PLATO, ARIEL:
https://www.youtube.com/watch?v=w8tx4bXm3Ko

“CHEOPS – the CHaracterising ExOPlanet Satellite – will target nearby, bright stars already known to have orbiting planets.”

I hope that includes Alpha Centauri. It’s a crying shame that the existence or otherwise of a planet or planets around Alpha Centauri B is still uncertain. It probably won’t.

CHEOPS is to be ready to launch in early 2019. The mission aims to bring an optical Ritchey–Chrétien telescope with an aperture of 30 cm, mounted on a standard small satellite platform, into a Sun-synchronous orbit of about 700 km (430 mi) altitude. For the planned mission duration of 3.5 years,

From https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10563/105631L/CHEOPS—a-space-telescope-for-ultra-high-precision-photometry/10.1117/12.2304164.full?SSO=1

“a large number of exoplanets have been discovered using dynamical (radial velocity) or photometric (transit) perturbations. This leaves us with essentially two populations of exoplanets, one for which we know the mass and one for which we know the radius with very little overlap. The goal of CHEOPS is to significantly increase the sample of objects for which both quantities are known.”

“CHEOPS will target host stars of super-Earth exoplanets detected from the ground by means of high-precision radial velocity surveys. It will also target transiting Neptune-like planets detected from the new generation ground-based transit surveys. Additional targets will come from the TESS satellite”

It will be looking at “Earth and super-Earth planets orbiting G5 stars with V-band magnitudes in the range 6 ≤ V ≤ 9 mag (and) Neptune-size planets orbiting K-type dwarf stars with V-band magnitudes as faint as V=12 mag”.

Target list may include (I’ve selected these from the list of bright stars with confirmed planets where the planet has been detected by Doppler shift:

beta Ursae Minoris – but perhaps not because it’s a Jupiter-like planet in a Mars-like orbit
Rho Coronae Borealis
18 Del
Kapteyn’s star
83 Leonis B
Gamma-1 Leonis
11 Com
iota Draconis
omi CrB
61 Vir
6 Lyn
tau Boo A

etc.

No. I still don’t understand CHEOPS. It seems to be looking for transits for planets already identified from Doppler Shift. But that’s a very hit or miss approach. There may be of the rough order of 1000 misses for every hit. It would be really important to get that target list, if it exists. One thing I do understand is that the timing of observation will be made to coincide with the time of the closest approach to transit of the planet already ascertained from Earth-based Doppler observations. But is it doing Doppler measurements as well or just transit measurements?

Slideshow of CHEOPS

http://geco.oeaw.ac.at/resources/cheops/talks/Benz.pdf

Name CHEOPS (CHaracterizing ExOPlanet Satellite)
Primary science goal Measure of the radius of planets transiting bright stars to 10% accuracy
Targets Known exoplanet host stars with a V-magnitude < 12 anywhere on the sky
Wavelength Visible range : 400 to 1100 nm
Telescope 30 cm effective aperture reflective on-axis telescope
Orbit LEO sun-synchronous, LTAN 6am, 700 km
Lifetime 3.5 years nominal, 5 years extended
launch readiness end 2018 (first launch opportunity as passenger)

Quality not quantity!

• science case is based on what precision photometry of a relatively small sample of well selected targets

Mission planning

• most targets will require time-critical observations, optimal scheduling is essential

Time of observation

• efficient single target observing mode requires the best possible knowledge of the ephemeris

(no kidding)

Still leaves a lot of questions unanswered.

Why use a 1 megapixel sensor if you’re going to discard all but the central 200*200?

What is this 50%, 20% interruptions thing? To do with can’t see closer than 120 degrees to the sun? eg. can’t see anything at the ecliptic poles because that’s always 90 degrees to the sun?

Not sure why so many imagette extractions. Wouldn’t just one after stacking suffice?

Why 2/3 southern hemisphere for 20% interruptions?

It doesn’t look as if there’s any doppler velocity measurements onboard, so it can’t measure radial velocity (which I initially thought was the aim).

CHEOPS

“The consortium target list will be published prior to the call and will be protected”

I hope by protected it mean that allocated time slots cannot be changed, rather than hidden behind a security wall.

> The first issue of the CHEOPS Reserved target List will comprise targets from the Guaranteed Time Observers Programme and will cover the full 3.5 years of the mission. The list will be maintained in a versioned database for which all entries and changes will be tracked and time-stamped/logged. It will be frozen at the time of the first (and subsequent) call(s). The list will be available to ESA to ensure transparency, but will not be provided to the Community as a whole.

> A dedicated tool will be available to query the Reserved Target List. It will report back on the status of a target. Scientists writing proposals to observe with CHEOPS will be required to use the tool, and to provide evidence that no targets in their proposals are on the list. Targets from guest observer proposals that are awarded observing time on CHEOPS will be added to the Reserved Target List and similarly blocked.

So both. allocated time slots AND hidden behind a security wall. Bad strategy ESA. Especially when coupled with the problem that Doppler planets tell us nothing about whether there could be a transit, so CHEOPS will spend most of its time finding nothing. What it will find is transits of planets previously detected as transiting planets from the ground, which won’t tell us all that much more than we already know, it won’t tell us the mass for instance.

Did you see the documentary on the ABC on Tuesday search for second Earth, part 1 of a 4 part series, the showed TESS on this.

Cymek said:

Did you see the documentary on the ABC on Tuesday search for second Earth, part 1 of a 4 part series, the showed TESS on this.

Missed that. What did it say?

mollwollfumble said:

Cymek said:

Did you see the documentary on the ABC on Tuesday search for second Earth, part 1 of a 4 part series, the showed TESS on this.

Missed that. What did it say?

Mentioned how it worked and its the latest in the planet finding satellites.
Was a good documentary, it started off with a future scenario in the 22nd century of the first interstellar spacecraft leaving to visit a star our various previous technologies indicated was a good second Earth candidate. I thought it would be one of the fluff documentaries because of that but it wasn’t. Showed more of the James Webb telescope as well, that’s an impressive piece of technology

Cymek said:

mollwollfumble said:

Cymek said:

Did you see the documentary on the ABC on Tuesday search for second Earth, part 1 of a 4 part series, the showed TESS on this.

Missed that. What did it say?

Mentioned how it worked and its the latest in the planet finding satellites.
Was a good documentary, it started off with a future scenario in the 22nd century of the first interstellar spacecraft leaving to visit a star our various previous technologies indicated was a good second Earth candidate. I thought it would be one of the fluff documentaries because of that but it wasn’t. Showed more of the James Webb telescope as well, that’s an impressive piece of technology

Yes, the James Webb is impressive. At first I complained (long and loud) about its failure as a replacement for Hubble because it couldn’t see UV at all, and can see blue with no more resolution than Hubble can, so the JWST images won’t be as nice as Hubble’s. Also because there were so many other IR telescopes springing up everywhere that it was beginning to look like the JWST would be obsolete before it was launched.

But I’ve changed my view now. There’s a lot more to see in space in IR than there is in UV, and the coronagraph on the JWST should prove excellent for finding dust, gas, asteroids and planets around stars.

Which reminds me. How does the FOV of the JWST compare with Hubble? How does the number of pixels of the JWST compare with Hubble? How does the IR range of JWST compare with that of the the most recent camera (with extended IR) on Hubble?

mollwollfumble said:

Cymek said:

mollwollfumble said:

Missed that. What did it say?

Mentioned how it worked and its the latest in the planet finding satellites.
Was a good documentary, it started off with a future scenario in the 22nd century of the first interstellar spacecraft leaving to visit a star our various previous technologies indicated was a good second Earth candidate. I thought it would be one of the fluff documentaries because of that but it wasn’t. Showed more of the James Webb telescope as well, that’s an impressive piece of technology

Yes, the James Webb is impressive. At first I complained (long and loud) about its failure as a replacement for Hubble because it couldn’t see UV at all, and can see blue with no more resolution than Hubble can, so the JWST images won’t be as nice as Hubble’s. Also because there were so many other IR telescopes springing up everywhere that it was beginning to look like the JWST would be obsolete before it was launched.

But I’ve changed my view now. There’s a lot more to see in space in IR than there is in UV, and the coronagraph on the JWST should prove excellent for finding dust, gas, asteroids and planets around stars.

Which reminds me. How does the FOV of the JWST compare with Hubble? How does the number of pixels of the JWST compare with Hubble? How does the IR range of JWST compare with that of the the most recent camera (with extended IR) on Hubble?

Correction. It’s worse than that. Not only can the JWST not see UV at all. It also can’t see blue or green or yellow at all. It may be able to see a bit of orange, but only because the shortest wavelength filter, centred on red, extends a little into both IR and orange ranges.

FOV for the JWST is 130 arcseconds. For the WFC3 on Hubble is 162 arcseconds. Hubble is better.

Hubble range on the WFC3 is 200 to 1700 nm. For the JWST the shortest wavelength camera NIRCam is 615 to 5000 nm. The JWST also extends out to 30000 mm. SPITZER was 3200 nm to 9500 nm. Herchel was 90000 mm and longer.

Pixels. Hubble WFC3 is 16 megapixels. NIRCam is 40 megapixels, of which 16 megapixels are for shorter wavelengths, so same as Hubble.

I wonder if it would make sense to create a satellite array were it’s a number of telescope/satellites tethered together but separated enough they don’t affect it each, each measuring/observing different wavelength and then processed and combined to form one image of all the data

Cymek said:

I wonder if it would make sense to create a satellite array were it’s a number of telescope/satellites tethered together but separated enough they don’t affect it each, each measuring/observing different wavelength and then processed and combined to form one image of all the data

With multiple cameras on the same satellite at different frequencies operating at the same time, something like this is happening already, but not with a satellite array.

I got to wonder how Hubble gyroscopes are going, given that the used to fail very often. No mention of failure in this website from Dec 2017 so I assume that they are all going ok. Below is the layout.

https://www.nasa.gov/content/goddard/hubble-space-telescope-pointing-control-system

Michael V said:

Tau.Neutrino said:

Experimental exoplanet-hunting CubeSat starts to prove itself in space

A small experimental CubeSat called the Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) has earned recognition for an ability to punch above its own weight. Awarded the Small Satellite Mission of the Year by the Small Satellite Technical Committee of the American Institute of Aeronautics and Astronautics’ (AIAA), the bread loaf-sized spacecraft is designed to show that small satellites can hunt for exoplanets just as larger space telescopes like Kepler can, and impressed after “demonstrat a significant improvement in the capability of small satellites.”

Nice. That really should go into the TESS thread for moll to see.

Done. Copied from the Chat thread.

:)

Michael V said:

Michael V said:

Tau.Neutrino said:

Experimental exoplanet-hunting CubeSat starts to prove itself in space

A small experimental CubeSat called the Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) has earned recognition for an ability to punch above its own weight. Awarded the Small Satellite Mission of the Year by the Small Satellite Technical Committee of the American Institute of Aeronautics and Astronautics’ (AIAA), the bread loaf-sized spacecraft is designed to show that small satellites can hunt for exoplanets just as larger space telescopes like Kepler can, and impressed after “demonstrat a significant improvement in the capability of small satellites.”

Nice. That really should go into the TESS thread for moll to see.

Done. Copied from the Chat thread.

:)

> for moll to see.

Yes. Very much appreciate that. The only astronomical cubesat telescope I know is Canada’s Humble Space Telescope (actually MOST for My Own Space Telescope).

Although I did hear of an earth observation cubesat telescope.

I would not have thought that the “Arcsecond Space Telescope” was possible. Extremely glad that it is.

mollwollfumble said:

Michael V said:

Michael V said:

Nice. That really should go into the TESS thread for moll to see.

Done. Copied from the Chat thread.

:)

> for moll to see.

Yes. Very much appreciate that. The only astronomical cubesat telescope I know is Canada’s Humble Space Telescope (actually MOST for My Own Space Telescope).

Although I did hear of an earth observation cubesat telescope.

I would not have thought that the “Arcsecond Space Telescope” was possible. Extremely glad that it is.

Compare that with Asteria. Asteria is smaller.

They are testing pointing technology and orbit change. There is no coronagraph or anything like that. Having a lens means it’s wide field. The pointing and orbit change is impressive. What startles me most is their ability to … the thermal control system. Holding the focal plane temperature accurate to a hundredth of a degree Kelvin.

I’d love to see the design specs for this. Every part of it.

Original JPL press release is at https://www.jpl.nasa.gov/cubesat/missions/asteria.php

See also

Background: The ASTERIA project, formerly called ExoplanetSat that was based on a 3U CubeSat mission, is motivated by the thought that no current mission has the capability to survey the nearest sun-like stars for an Earth analog. The best way to monitor the brightest sun-like stars (0 < V < 6) for long-duration transiting exoplanets is by a targeted star search; the brightest stars are too widely separated across the sky for a single telescope to continuously monitor. A fleet of dozens of identical ASTERIA spacecraft would be ideal to each monitor one star at a time, instead of a single space telescope surveying thousands of stars simultaneously. The detailed properties of each target star are well known in advance.

Heck, that’s good . We can finally watch alpha Centauri and Proxima Centauri, tau Ceti and epsilon Eridani. See if their alien inhabitants are up to no good.