Exhibit 10.1





THIS CONVERTIBLE PROMISSORY NOTE (THIS
“NOTE”) AND THE SECURITIES INTO WHICH IT MAY BE CONVERTED HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
AS AMENDED (THE “SECURITIES ACT”), OR UNDER THE SECURITIES LAWS OF ANY STATE. THESE SECURITIES ARE SUBJECT TO RESTRICTIONS
ON TRANSFERABILITY AND RESALE. THIS NOTE HAS BEEN ACQUIRED FOR INVESTMENT ONLY AND MAY NOT BE SOLD, TRANSFERRED OR ASSIGNED EXCEPT
AS PERMITTED UNDER THE SECURITIES ACT AND THE APPLICABLE STATE SECURITIES LAWS, PURSUANT TO REGISTRATION OR EXEMPTION THEREFROM.
INVESTORS SHOULD BE AWARE THAT THEY MAY BE REQUIRED TO BEAR THE FINANCIAL RISKS OF THIS INVESTMENT FOR AN INDEFINITE PERIOD OF
TIME. THE COMPANY AND THE SECURITIES INTO WHICH IT MAY BE CONVERTED MAY REQUIRE AN OPINION OF COUNSEL REASONABLY SATISFACTORY IN
FORM, SCOPE AND SUBSTANCE TO THE COMPANY TO THE EFFECT THAT ANY SALE OR OTHER DISPOSITION IS IN COMPLIANCE WITH THE SECURITIES
ACT AND ANY APPLICABLE STATE SECURITIES LAWS.


SENTINEL ENERGY SERVICES INC. 


CONVERTIBLE PROMISSORY NOTE 


	 	 	 
	
        Principal Amount: Not to Exceed $1,500,000

        (See Schedule A)
	 	Dated as of March 1, 2019


FOR VALUE RECEIVED
and subject to the terms and conditions set forth herein, Sentinel Energy Services Inc., a Delaware corporation (the “Maker”),
promises to pay to the order of Sentinel Management Holdings, LLC or its registered assigns or successors in interest (the “Payee”),
or order, the principal balance as set forth on Schedule A hereto in lawful money of the United States of America; which
schedule shall be updated from time to time by the parties hereto to reflect all advances and readvances outstanding under this
Note; provided that at no time shall the aggregate of all advances and readvances outstanding under this Note exceed one million
five hundred thousand dollars ($1,500,000). Any advance hereunder shall be made by the Payee upon receipt of a written request
of the Maker and shall be set forth on Schedule A. All payments on this Note shall be made by check or wire transfer of
immediately available funds or as otherwise determined by the Maker to such account as the Payee may from time to time designate
by written notice in accordance with the provisions of this Note.


1. Principal.
All unpaid principal under this Note shall be due and payable in full on the earlier of (i) November 7, 2019 and (ii) the effective
date of a merger, capital stock exchange, asset acquisition, stock purchase, reorganization or similar business combination, involving
the Company and one or more businesses (the “Business Combination”) (such earlier date, the “Maturity
Date”), unless accelerated upon the occurrence of an Event of Default (as defined below). Any outstanding principal
amount to date under this Note may be prepaid at any time by the Maker, at its election and without penalty; provided, however,
that Payee shall have a right to first convert such principal balance pursuant to Section 5 below upon notice of such prepayment.






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2. Interest.
No interest shall accrue on the unpaid balance of this Note.


3. Application
of Payments. All payments shall be applied first to payment in full of any costs incurred in the collection of any sum due
under this Note, including (without limitation) reasonable attorney’s fees, then to the payment in full of any late charges
and finally to the reduction of the unpaid principal balance of this Note.


4. Events of
Default. The occurrence of any of the following shall constitute an event of default (“Event of Default”):


(a) Failure to
Make Required Payments. Failure by the Maker to pay the principal amount due pursuant to this Note within five (5) business
days of the date specified above or issue warrants pursuant to Paragraph 5 hereof, if so elected by the Payee.


 


(b) Voluntary Bankruptcy,
Etc. The commencement by the Maker of a voluntary case under any applicable bankruptcy, insolvency, reorganization, rehabilitation
or other similar law, or the consent by it to the appointment of or taking possession by a receiver, liquidator, assignee, trustee,
custodian, sequestrator (or other similar official) of the Maker or for any substantial part of its property, or the making by
it of any assignment for the benefit of creditors, or the failure of the Maker generally to pay its debts as such debts become
due, or the taking of corporate action by the Maker in furtherance of any of the foregoing.


(c) Involuntary
Bankruptcy, Etc. The entry of a decree or order for relief by a court having jurisdiction in the premises in respect of the
Maker in an involuntary case under any applicable bankruptcy, insolvency or other similar law, or appointing a receiver, liquidator,
assignee, custodian, trustee, sequestrator (or similar official) of the Maker or for any substantial part of its property, or ordering
the winding-up or liquidation of its affairs, and the continuance of any such decree or order unstayed and in effect for a period
of sixty (60) consecutive days.


5. Conversion



(a) Optional Conversion.
At the option of the Payee, at any time on or prior to the Maturity Date, any amounts outstanding under this Note (or any portion
thereof), up to $1,500,000 in the aggregate, may be converted into warrants to purchase shares of Class A common stock of the Maker
(“Class A Common Stock”) at a conversion price (the “Conversion Price”)
equal to $1.50 per warrant (“Warrants”). If the Payee elects such conversion, the terms of such Warrants
issued in connection with such conversion shall be identical to the warrants issued to the Payee in the private placement that
closed on November 7, 2017 (the “Private Placement Warrants”) in connection with the Maker’s initial
public offering that closed on November 7, 2017 (the “IPO”), including that each Warrant shall entitle
the holder thereof to purchase one share of Class A Common Stock at a price of $11.50 per share, subject to the same adjustments
applicable to the Private Placement Warrants. Before this Note may be converted under this Section 5(a), the Payee shall surrender
this Note, duly endorsed, at the office of the Maker and shall state therein the amount of the unpaid principal of this Note to
be converted and the name or names in which the certificates for Warrants are to be issued (or the book-entries to be made to reflect
ownership of such Warrants with the Maker’s transfer agent). The conversion shall be deemed to have been made immediately
prior to the close of business on the date of the surrender of this Note and the person or persons entitled to receive the Warrants
upon such conversion shall be treated for all purposes as the record holder or holders of such Warrants as of such date. Each such
newly issued Warrant shall include a restricted legend that contemplates the same restrictions as the Private Placement Warrants.
The Warrants and shares of Class A Common Stock issuable upon exercise of the Warrants shall constitute “Registrable Securities”
pursuant to that certain Registration Rights Agreement, dated November 2, 2017, among the Maker, the Payee and certain other security
holders named therein.


 



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(b) Remaining
Principal. All accrued and unpaid principal of this Note that is not then converted into Warrants, shall continue to remain
outstanding and to be subject to the conditions of this Note.


(c) Fractional
Warrants; Effect of Conversion. No fractional Warrants shall be issued upon conversion of this Note. In lieu of any fractional
Warrants to the Payee upon conversion of this Note, the Maker shall pay to the Payee an amount equal to the product obtained by
multiplying the Conversion Price by the fraction of a Warrant not issued pursuant to the previous sentence. Upon conversion of
this Note in full and the payment of any amounts specified in this Section 5(c), this Note shall be cancelled and void without
further action of the Maker or the Payee, and the Maker shall be forever released from all its obligations and liabilities under
this Note.


6. Remedies.



(a) Upon the occurrence
of an Event of Default specified in Section 4(a) hereof, the Payee may, by written notice to the Maker, declare this Note to be
due immediately and payable, whereupon the unpaid principal amount of this Note, and all other amounts payable thereunder, shall
become immediately due and payable without presentment, demand, protest or other notice of any kind, all of which are hereby expressly
waived, anything contained herein or in the documents evidencing the same to the contrary notwithstanding.


(b) Upon the occurrence
of an Event of Default specified in Sections 4(b) or 4(c), the unpaid principal balance of this Note, and all other sums payable
with regard to this Note, shall automatically and immediately become due and payable, in all cases without any action on the part
of the Payee.


7. Waivers.
The Maker and all endorsers and guarantors of, and sureties for, this Note waive presentment for payment, demand, notice of dishonor,
protest, and notice of protest with regard to the Note, all errors, defects and imperfections in any proceedings instituted by
the Payee under the terms of this Note, and all benefits that might accrue to the Maker by virtue of any present or future laws
exempting any property, real or personal, or any part of the proceeds arising from any sale of any such property, from attachment,
levy or sale under execution, or providing for any stay of execution, exemption from civil process, or extension of time for payment;
and the Maker agrees that any real estate that may be levied upon pursuant to a judgment obtained by virtue hereof, on any writ
of execution issued hereon, may be sold upon any such writ in whole or in part in any order desired by the Payee.


8. Unconditional
Liability. The Maker hereby waives all notices in connection with the delivery, acceptance, performance, default, or enforcement
of the payment of this Note, and agrees that its liability shall be unconditional, without regard to the liability of any other
party, and shall not be affected in any manner by any indulgence, extension of time, renewal, waiver or modification granted or
consented to by the Payee, and consents to any and all extensions of time, renewals, waivers, or modifications that may be granted
by the Payee with respect to the payment or other provisions of this Note, and agrees that additional makers, endorsers, guarantors,
or sureties may become parties hereto without notice to the Maker or affecting the Maker’s liability hereunder.






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9. Notices.
All notices, statements or other documents which are required or contemplated by this Note shall be in writing and delivered (i)
personally or sent by first class registered or certified mail, overnight courier service to the address designated in writing,
(ii) by facsimile to the number most recently provided to such party or such other address or fax number as may be designated in
writing by such party, or (iii) by electronic mail, to the electronic mail address most recently provided to such party or such
other electronic mail address as may be designated in writing by such party. Any notice or other communication so transmitted shall
be deemed to have been given on the day of delivery, if delivered personally or by facsimile or electronic transmission; one (1)
business day after delivery to an overnight courier service; or five (5) days after mailing if sent by first class registered or
certified mail.


10. Construction.
THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF NEW YORK APPLICABLE TO CONTRACTS MADE AND TO BE PERFORMED
WITHIN THE STATE OF NEW YORK.


11. Severability.
Any provision contained in this Note which is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be
ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any
such prohibition or unenforceability in any jurisdiction shall not invalidate or render unenforceable such provision in any other
jurisdiction.


12. Trust Waiver.
Notwithstanding anything herein to the contrary, the Payee hereby waives any and all right, title, interest or claim of any kind
(“Claim”) in or to any distribution of or from the trust account established in which the proceeds of
the IPO conducted by the Maker (including the deferred underwriters discounts and commissions) and certain proceeds of the sale
of the Private Placement Warrants were deposited, as described in greater detail in the registration statement and prospectus filed
with the U.S. Securities and Exchange Commission in connection with the IPO on November 7, 2017, and hereby agrees not to seek
recourse, reimbursement, payment or satisfaction for any Claim against the trust account for any reason whatsoever.


13. Amendment;
Waiver. Any amendment hereto or waiver of any provision hereof may be made with, and only with, the written consent of the
Maker and the Payee.


14. Successors
and Assigns. Subject to the restrictions on transfer in Sections 15 and 16 below, the rights and obligations of the Maker and
the Payee hereunder shall be binding upon and benefit the successors, assigns, heirs, administrators and transferees of any party
hereto (by operation of law or otherwise) with the prior written consent of the other party hereto and any attempted assignment
without the required consent shall be void.






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15. Transfer
of this Note or Securities Issuable on Conversion. With respect to any sale or other disposition of this Note or securities
into which this Note may be converted, the Payee shall give written notice to the Maker prior thereto, describing briefly the manner
thereof, together with (i) except for a Permitted Transfer, in which case the requirements in this clause (i) shall not apply,
a written opinion reasonably satisfactory to the Maker in form and substance from counsel reasonably satisfactory to the Maker
to the effect that such sale or other distribution may be effected without registration or qualification under any federal or state
law then in effect and (ii) a written undertaking executed by the desired transferee reasonably satisfactory to the Maker in form
and substance agreeing to be bound by the restrictions on transfer contained herein. Upon receiving such written notice, reasonably
satisfactory opinion, or other evidence, and such written acknowledgement, the Maker, as promptly as practicable, shall notify
the Payee that the Payee may sell or otherwise dispose of this Note or such securities, all in accordance with the terms of the
note delivered to the Maker. If a determination has been made pursuant to this Section 15 that the opinion of counsel for the Payee,
or other evidence, or the written acknowledgment from the desired transferee, is not reasonably satisfactory to the Maker, the
Maker shall so notify the Payee promptly after such determination has been made. Each Note thus transferred shall bear a legend
as to the applicable restrictions on transferability in order to ensure compliance with the Securities Act, unless in the opinion
of counsel for the Maker such legend is not required in order to ensure compliance with the Securities Act. The Maker may issue
stop transfer instructions to its transfer agent in connection with such restrictions. Subject to the foregoing, transfers of this
Note shall be registered upon registration on the books maintained for such purpose by or on behalf of the Maker. Prior to presentation
of this Note for registration of transfer, the Maker shall treat the registered holder hereof as the owner and holder of this Note
for the purpose of receiving all payments of principal hereon and for all other purposes whatsoever, whether or not this Note shall
be overdue and the Maker shall not be affected by notice to the contrary. For purposes hereof “Permitted Transfer”
shall have the same meaning as any transfer that would be permitted for the Private Placement Warrants under the Letter Agreement,
dated November 2, 2017, among the Maker, the Payee and the other parties thereto.


16. Acknowledgment.
The Payee is acquiring this Note for investment for its own account, not as a nominee or agent, and not with a view to, or for
resale in connection with, any distribution thereof. The Payee understands that the acquisition of this Note involves substantial
risk. The Payee has experience as an investor in securities of companies and acknowledges that it is able to fend for itself, can
bear the economic risk of its investment in this Note, and has such knowledge and experience in financial and business matters
that it is capable of evaluating the merits and risks of this investment in this Note and protecting its own interests in connection
with this investment.


[Signature Page Follows]


 



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IN WITNESS WHEREOF,
the Maker, intending to be legally bound hereby, has caused this Note to be duly executed by the undersigned as of the day and
year first above written.


 


	SENTINEL ENERGY SERVICES INC.
	 	
         

        

	By:	 	
        /s/ Krishna Shivram

	Name:	 	Krishna Shivram
	Title:	 	Chief Executive Officer



 


Acknowledged and agreed as of the date first above written.





	SENTINEL MANAGEMENT HOLDINGS, LLC
	 	
         

        

	By:	 	
        /s/ Charles S. Leykum

	Name:	 	Charles S. Leykum 
	Title:	 	Managing Member


 





 


[Signature Page to Convertible Promissory
Note]







 






    	 		 



     


    

 





 


SCHEDULE A 


Subject to the terms
and conditions set forth in the Note to which this schedule is attached to, the principal balance due under the Note shall be set
forth in the table below and shall be updated from time to time to reflect all advances and readvances outstanding under the Note.


	 	 	 	 	 	 	 
	
        Date
	 	
        Drawing
	 	
        Description
	 	
        Principal
        Balance