<p>From <a href="https://jwst-docs.stsci.edu/jwst-general-support/jwst-observing-overheads-and-time-accounting-overview/jwst-slew-times-and-overheads" rel="noreferrer">JWST Slew Times and Overheads</a>,</p>
<blockquote>
<p>The Astronomer's Proposal Tool (APT) charges time to JWST observations for telescope slews of various kinds as a function of slew distance.</p>
</blockquote>
<p>Before science observations for some experiment can commence, the JWST needs to change its orientation, stabilize its orientation, and acquire a guide star. All of this takes time. The &quot;charge time&quot; includes this overhead time plus the time spent collective scientific data.</p>

CC BY-SA 4.0
2022-03-16T16:28:29.827Z
2022-03-16T16:28:29.827Z
David Hammen
<p>&quot;Charged time&quot; includes all of the overhead associated with carrying out the observing program, rather than just the open shutter exposure time. The overheads include slewing time, acquisition of guide stars, configuring filterwheels, grisms etc and readout times. An overview is given in <a href="https://jwst-docs.stsci.edu/jwst-general-support/jwst-observing-overheads-and-time-accounting-overview/jwst-observing-overheads-summary" rel="noreferrer">JWST Observing Overheads Summary</a> which links to more detailed information. The APT tool which is used by astronomers to prepare proposals for JWST, has a &quot;Smart Accounting&quot; feature that will estimate the overheads for you based on your planned observing.</p>

CC BY-SA 4.0
2022-03-16T16:30:39.513Z
2022-03-16T16:30:39.513Z
astrosnapper
<p>In the Early Release Science proposals for the JWST such as <a href="https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1288-berne.pdf" rel="nofollow noreferrer">this one</a>, there is a &quot;Charged Time&quot; rubric. What is it? What is done during this time?</p>

<space-telescope><james-webb-space-telescope>
What is "Charged time" in JWST ERS proposals?
usernumber
# What is "Charged time" in JWST ERS proposals?

(Asked by: username_0 on 2022-03-16)

In the Early Release Science proposals for the JWST such as [this one](https://www.stsci.edu/files/live/sites/www/files/home/jwst/news-events/news/pre-2018/_documents/ers-1288-berne.pdf), there is a "Charged Time" rubric. What is it? What is done during this time?

**Tags:** space-telescope, james-webb-space-telescope

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## 2 answers

### Answer by username_2 on 2022-03-16. Score: 8 | Accepted answer

"Charged time" includes all of the overhead associated with carrying out the observing program, rather than just the open shutter exposure time. The overheads include slewing time, acquisition of guide stars, configuring filterwheels, grisms etc and readout times. An overview is given in [JWST Observing Overheads Summary](https://jwst-docs.stsci.edu/jwst-general-support/jwst-observing-overheads-and-time-accounting-overview/jwst-observing-overheads-summary) which links to more detailed information. The APT tool which is used by astronomers to prepare proposals for JWST, has a "Smart Accounting" feature that will estimate the overheads for you based on your planned observing.


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### Answer by username_1 on 2022-03-16. Score: 5

From [JWST Slew Times and Overheads](https://jwst-docs.stsci.edu/jwst-general-support/jwst-observing-overheads-and-time-accounting-overview/jwst-slew-times-and-overheads),

> The Astronomer's Proposal Tool (APT) charges time to JWST observations for telescope slews of various kinds as a function of slew distance.

Before science observations for some experiment can commence, the JWST needs to change its orientation, stabilize its orientation, and acquire a guide star. All of this takes time. The "charge time" includes this overhead time plus the time spent collective scientific data.


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