NASA’s Nancy Grace Roman Space Telescope is getting closer and closer to its launch date in 2025. This Hubble-class infrared wide-field telescope will help astronomers discover the nature of dark energy, discover planets, and conduct large-area nocturnal surveys in the sky.
But even with its power, the telescope will only be able to examine planets to a limited extent.
A team of engineers suggests flying a follow-up mission to Nancy Grace: a Starshade. This petal-shaped spaceship could fly in formation with the telescope, blocking the light from stars and helping it see the fainter planets nearby.
An extraordinary telescope is getting an upgrade? That seems like a win-win situation.
One of the next observatories designed to improve mankind’s understanding of the cosmos is the Nancy Grace Roman Space Telescope (NGRST), formerly known as the Wide Field InfraRed Survey Telescope (WFIRST). The name change should be the legacy of Dr. Honoring Nancy Grace Roman, known today as the “Mother of Hubble” for her work in making Hubble a reality. She created NASA’s space astronomy program, became NASA’s first female executive, and was NASA’s first female director of astronomy in the 1960s and 1970s. (Rehm)
“Nancy Grace Roman is a role model. We name this mission after Nancy Grace Roman because of her great accomplishments. I think it really helped the younger woman [sic] To see that a woman can succeed, a woman can be the best, ”said Dr. Julie McEnery, Assistant Project Scientist for the Roman Space Telescope. (Rehm)
NGRST has a planned mission time of five years, but as always we can hope for a longer duration. The currently planned start date is 2025 and starts with an EELV (Evolved Expendable Launch Vehicle) from Cape Canaveral. It is directed to the second Sun-Earth L2 Lagrange point, which is directly across from the Sun on the other side of the moon. This location is ideal for keeping instruments cool enough that the observatory can collect 10 times the data Hubble can handle. During its five-year mission, it is expected to measure light from a billion galaxies.
Artist’s impression of the Nancy Grace (formerly WFIRST) Roman Space Telescope. Photo credit: NASA / GSFC
That ranges from hundreds of billions to two trillion galaxies in the universe just to put things in perspective. (Strickland)
This telescope is as impressive as it is.
The NASA observatory will have two instruments on board, the Wide Field Instrument and the Coronagraph Instrument. The wide field instrument has a 300 megapixel camera that offers a 100 times larger field of view than the Hubble infrared instrument. This equates to more sky in less time. In five years it will have imaged over 50 times as much sky as Hubble observed in the first thirty years.
The Coronagraph Instrument (CGI) will perform high-contrast imaging and spectroscopy of dozen of nearby exoplanets. It will remove the glare from nearby stars and allow it to see planets that are nearly a billion times fainter than their host star. The results of the CGI will help future missions observe and characterize rocky planets in the habitable zone of the stars (an area where the temperature is at the right level for liquid water to form, which is believed to be a key component of life becomes). (Krishna)
The NGRST will conduct near-infrared surveys to explore nearby stars and distant galaxies. The observatory will help find dark matter and energy, and a microlens survey is expected to find ~ 2,600 exoplanets. That is all well and good.
But it could be better.
Artist’s impression of a star’s shadow that blocks the starlight from a nearby planetary system and enables images of earth-sized planets in the habitable zones around sun-like stars. (Photo credit: Jay Wong, Los Angeles, California.)
There is a proposal by Andrew Romero-Wolf et al. To develop the so-called Starshade Rendezvous Probe. This would be a 26-meter-long free-flying device that the Nancy Grace Roman Space Telescope could use to detect Earth-like exoplanets in the habitable zones of their host star and increase sensitivity in order to spectrally characterize Earth-like exoplanets. It would also be able to detect the dust surrounding Earth-like exoplanets. This dust has a small mass but a large area that is easier to observe than the planet itself.
Planets are about 10 billion times weaker than the light from their parent star. Star shadows block this light, much like a solar eclipse. During a solar eclipse, it’s easier to see what’s happening around the sun without blinding it. If a star shadow is used, the planets around a star can be mapped directly, and the atmospheres of exoplanets can also be analyzed.
The star shadow is not a new concept. NASA has already worked on a petal-shaped version. This shape was developed to reduce the bending of light waves and to image planets without being overwhelmed by the parent starlight. (Rodriguez) Northrop Grumman is helping develop the star’s shadow, which is taller than a 15-story building and would fly 20,000 to 40,000 kilometers from his observatory. It is expected to help discover extrasolar planets within 50 light years of us. (Northrop Grumman)
However, there are some hurdles to overcome. This is technology that has never been built before and requires very detailed engineering. The perfect alignment of the star shadow and the observatory is just one of the difficult tasks that engineers face. JPL engineer Michael Bottom put it best when he said, “If the star shadow were reduced to the size of a coaster, the telescope would be the size of an eraser and they would be about 60 miles apart [100 kilometers]. Now imagine that these two objects are floating freely in space. Both of them experience these small pulls and bumps from gravity and other forces, and over this distance we try to align them both to within about 2 millimeters. “(NASA)
And then there is the unfolding of the star shadow. The video above shows what the star shadow needs to do to be properly deployed, and these are just the first little steps. When a star screen is ready for a mission, one can only imagine how many complicated steps, motors, and actuators it would take to use it properly. If the process of unfolding the solar shield of the James Webb Space Telescope is an indicator, it is not an easy task.
Even with the next flagship observatory like HabEx or Luvoir, there won’t be another observatory that can recognize Earth-like exoplanets in the next ten years. The hope is that this Starshade Rendezvous probe will launch three years after the start of the NGRST mission and that it will have at least two years to discover these Earth-like exoplanets.
Our understanding of the universe expands with each new observatory that is brought into space. Technology like the proposed star shadow will be of great help in expanding our knowledge.
ArXiv: Starshade Rendezvous: Exoplanet Sensitivity and Observation Strategy
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NASA WFIRST telescope renamed after ‘Mother of Hubble’ Nancy Grace Roman
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Star shadow – key tool in finding Earth-like planets
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